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Polymers, Volume 12, Issue 12 (December 2020) – 308 articles

Cover Story (view full-size image): Heterografted copolymers varied by ratio of PEG/PCL side chains are proposed as carriers designed for the delivery of substances applicable in cosmetology that include dermatological problems. The self-assembling copolymers formed micelles with the ability to encapsulate cosmetic substances, e.g., arbutin, vitamin C, 4-n-butylresorcinol. The nature of the loaded substance interacting with polymer matrix is crucial in kinetic release profiles. The permeation tests of the active substance released through a membrane acting as human skin in Franz chambers indicated a moderate diffusion into solution and remained in the membrane, which is satisfactory for most cosmetic applications. View this paper.
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8 pages, 2144 KiB  
Article
Two-Dimensional Piezoresistive Response and Measurement of Sensitivity Factor of Polymer-Matrix Carbon Fiber Mat
by Min Wu, Li Huang, Xiaoyu Zhang, Jianzhong Chen and Yong Lv
Polymers 2020, 12(12), 3072; https://doi.org/10.3390/polym12123072 - 21 Dec 2020
Cited by 1 | Viewed by 2226
Abstract
Based on the piezoresistive effect, the piezoresistive constitutive relation of a carbon fiber mat under orthogonal strain was deduced. Considering the Poisson effect, the piezoresistive responses and measurement of the sensitivity factor of a polymer-matrix carbon fiber mat under bidirectional strain were studied [...] Read more.
Based on the piezoresistive effect, the piezoresistive constitutive relation of a carbon fiber mat under orthogonal strain was deduced. Considering the Poisson effect, the piezoresistive responses and measurement of the sensitivity factor of a polymer-matrix carbon fiber mat under bidirectional strain were studied by a two-times uniaxial tension loading method in different directions, which was pasted in the center area of a cruciform aluminum substrate. The relations between the resistance change rate and the orthogonal strains were established, the reasonability of which was confirmed by comparison with the experimental results. The results show that the longitudinal piezoresistive sensitivity factor C11 is 21.55, and the lateral piezoresistive sensitivity factor C12 is 24.15. Using these factors, the resistance change rate of another polymer-matrix carbon mat was predicted, which was made by the same technique, and the error between the predicted and the experimental results was 1.3% in the longitudinal direction and 6.1% in the lateral direction. Full article
(This article belongs to the Special Issue Reinforced Polymer Composites II)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Schematic diagram of electrode layout.</p> Full article ">Figure 2
<p>Front and back of the specimen: (<b>a</b>) polymer-matrix carbon mat attachment position on the front; (<b>b</b>) strain gauge attachment position on the back.</p> Full article ">Figure 3
<p>Device diagram of loading: (<b>a</b>) loading along the 1st-direction; (<b>b</b>) loading along the 2nd-direction.</p> Full article ">Figure 4
<p>Test curve of sample No. 1: (<b>a</b>) loading along the 1st-direction; (<b>b</b>) loading along the 2nd-direction.</p> Full article ">Figure 5
<p>Test curve of sample No. 2: (<b>a</b>) loading along the 1st-direction; (<b>b</b>) loading along the 2nd-direction.</p> Full article ">Figure 6
<p>Schematic diagram of the conductive network of the carbon fiber mat: (<b>a</b>) before loading; (<b>b</b>) after loading.</p> Full article ">Figure 7
<p>Test curve of sample No. 3: (<b>a</b>) loading along the 1st-direction; (<b>b</b>) loading along the 2nd-direction.</p> Full article ">
18 pages, 4501 KiB  
Article
Study on the Anti-Biodegradation Property of Tunicate Cellulose
by Yanan Cheng, Ajoy Kanti Mondal, Shuai Wu, Dezhong Xu, Dengwen Ning, Yonghao Ni and Fang Huang
Polymers 2020, 12(12), 3071; https://doi.org/10.3390/polym12123071 - 21 Dec 2020
Cited by 15 | Viewed by 3320
Abstract
Tunicate is a kind of marine animal, and its outer sheath consists of almost pure Iβ crystalline cellulose. Due to its high aspect ratio, tunicate cellulose has excellent physical properties. It draws extensive attention in the construction of robust functional materials. However, [...] Read more.
Tunicate is a kind of marine animal, and its outer sheath consists of almost pure Iβ crystalline cellulose. Due to its high aspect ratio, tunicate cellulose has excellent physical properties. It draws extensive attention in the construction of robust functional materials. However, there is little research on its biological activity. In this study, cellulose enzymatic hydrolysis was conducted on tunicate cellulose. During the hydrolysis, the crystalline behaviors, i.e., crystallinity index (CrI), crystalline size and degree of polymerization (DP), were analyzed on the tunicate cellulose. As comparisons, similar hydrolyses were performed on cellulose samples with relatively low CrI, namely α-cellulose and amorphous cellulose. The results showed that the CrI of tunicate cellulose and α-cellulose was 93.9% and 70.9%, respectively; and after 96 h of hydrolysis, the crystallinity, crystalline size and DP remained constant on the tunicate cellulose, and the cellulose conversion rate was below 7.8%. While the crystalline structure of α-cellulose was significantly damaged and the cellulose conversion rate exceeded 83.8% at the end of 72 h hydrolysis, the amorphous cellulose was completely converted to glucose after 7 h hydrolysis, and the DP decreased about 27.9%. In addition, tunicate cellulose has high anti-mold abilities, owing to its highly crystalized Iβ lattice. It can be concluded that tunicate cellulose has significant resistance to enzymatic hydrolysis and could be potentially applied as anti-biodegradation materials. Full article
(This article belongs to the Section Biobased and Biodegradable Polymers)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Anti-mold experiment process of tunicate cellulose: (<b>a</b>) initial growth of mold and (<b>b</b>) growth of mold at time, t.</p> Full article ">Figure 2
<p>XRD patterns of tunicate cellulose: (<b>a</b>) original XRD pattern and (<b>b</b>) peak separation results.</p> Full article ">Figure 3
<p>XRD patterns of α-cellulose: (<b>a</b>) original XRD patterns and (<b>b</b>) peak separation results.</p> Full article ">Figure 4
<p>Patterns of amorphous cellulose.</p> Full article ">Figure 5
<p>FTIR spectra of tunicate, pulp <span class="html-italic">α</span> and amorphous cellulose.</p> Full article ">Figure 6
<p>The XRD pattern of tunicate cellulose after enzymatic hydrolysis.</p> Full article ">Figure 7
<p>The XRD pattern of α-cellulose after enzymatic hydrolysis.</p> Full article ">Figure 8
<p>The variations of <span class="html-italic">CrI</span> and average crystallite size (<span class="html-italic">I<sub>hkl</sub></span>) of tunicate cellulose during the enzymatic hydrolysis.</p> Full article ">Figure 9
<p>The variations of <span class="html-italic">CrI</span> and average crystallite size (<span class="html-italic">I<sub>hkl</sub></span>) of α-cellulose during the enzymatic hydrolysis.</p> Full article ">Figure 10
<p>The cellulose conversion from various crystalline celluloses during enzymatic hydrolysis.</p> Full article ">Figure 11
<p>TEM images of (<b>a</b>) tunicate cellulose nanocrystals and (<b>b</b>) α-cellulose nanocrystal.</p> Full article ">Figure 12
<p>Anti-mold effect of tunicate cellulose nanocrystals and α-cellulose nanocrystals.</p> Full article ">Figure 13
<p>Antibacterial effect of different concentrations of tunicate cellulose nanocrystals.</p> Full article ">
15 pages, 3181 KiB  
Article
Calcined Co(II)-Triethylenetetramine, Co(II)- Polyaniline-Thiourea as the Cathode Catalyst of Proton Exchanged Membrane Fuel Cell
by Wen-Yao Huang, Li-Cheng Jheng, Tar-Hwa Hsieh, Ko-Shan Ho, Yen-Zen Wang, Yi-Jhun Gao and Po-Hao Tseng
Polymers 2020, 12(12), 3070; https://doi.org/10.3390/polym12123070 - 21 Dec 2020
Cited by 9 | Viewed by 3042
Abstract
Triethylenetetramine (TETA) and thiourea complexed Cobalt(II) (Co(II)) ions are used as cathode catalysts for proton exchanged membrane fuel cells (PEMFCs) under the protection of polyaniline (PANI) which can become a conducting medium after calcination. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) [...] Read more.
Triethylenetetramine (TETA) and thiourea complexed Cobalt(II) (Co(II)) ions are used as cathode catalysts for proton exchanged membrane fuel cells (PEMFCs) under the protection of polyaniline (PANI) which can become a conducting medium after calcination. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra clearly reveal the presence of typical carbon nitride and sulfide bonds of the calcined Nitrogen (N)- or Sulfur (S)-doped co-catalysts. Clear (002) and (100) planes of carbon-related X-ray diffraction patterns are found for co-catalysts after calcination, related to the formation of a conducting medium after the calcination of PANI. An increasing intensity ratio of the D to G band of the Raman spectra reveal the doping of N and S elements. More porous surfaces of co-catalysts are found in scanning electronic microscopy (SEM) micropictures when prepared in the presence of both TETA and thiourea (CoNxSyC). Linear sweep voltammetry (LSV) curves show the highest reducing current to be 4 mAcm−2 at 1600 rpm for CoNxSyC, indicating the necessity for both N- and S-doping. The membrane electrode assemblies (MEA) prepared with the cathode made of CoNxSyC produces the highest maximum power density, close to 180 mW cm−2. Full article
(This article belongs to the Special Issue Functional and Conductive Polymer Thin Films II)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Fourier-transform infrared spectroscopy (FTIR) spectra of various co-catalysts.</p> Full article ">Figure 2
<p>X-ray photoelectron spectroscopy (XPS) spectra of (<b>a</b>) N1s of all co-catalysts (<b>b</b>) S2p of CoSyC (<b>c</b>) S<sub>2p</sub> of CoNxSyC (<b>d</b>) Comparing S<sub>2p</sub> of CoSyC with CoNxSyC.</p> Full article ">Figure 3
<p>X-ray diffraction patterns of various co-catalysts.</p> Full article ">Figure 4
<p>Raman spectra of various co-catalysts.</p> Full article ">Figure 5
<p>Scanning electronic microscopy (SEM) micropictures of (<b>a</b>) Co–C (<b>b</b>) CoNxC (<b>c</b>) CoSyC (<b>d</b>) CoNxSyC.</p> Full article ">Figure 6
<p>Linear sweep voltammetry (LSV) curves at all rpms of (<b>a</b>) CoNxC (<b>b</b>) CoSyC (<b>c</b>) CoNxSyC (<b>d</b>) LSV curves at 1600 rpm of all catalysts.</p> Full article ">Figure 7
<p>Power and current densities of single cells made of various co-catalyst cathodes.</p> Full article ">Scheme 1
<p>Preparing diagram of various co-catalysts.</p> Full article ">Scheme 2
<p>Electrocatalytic mechanism of N-, S-doped co-catalysts.</p> Full article ">Scheme 3
<p>ORR in the cathode catalyzed by CoNxSyC.</p> Full article ">
18 pages, 5014 KiB  
Article
Robustness of Empirical Vibration Correlation Techniques for Predicting the Instability of Unstiffened Cylindrical Composite Shells in Axial Compression
by Eduards Skukis, Gints Jekabsons, Jānis Andersons, Olgerts Ozolins, Edgars Labans and Kaspars Kalnins
Polymers 2020, 12(12), 3069; https://doi.org/10.3390/polym12123069 - 21 Dec 2020
Cited by 5 | Viewed by 2734
Abstract
Thin-walled carbon fiber reinforced plastic (CFRP) shells are increasingly used in aerospace industry. Such shells are prone to the loss of stability under compressive loads. Furthermore, the instability onset of monocoque shells exhibits a pronounced imperfection sensitivity. The vibration correlation technique (VCT) is [...] Read more.
Thin-walled carbon fiber reinforced plastic (CFRP) shells are increasingly used in aerospace industry. Such shells are prone to the loss of stability under compressive loads. Furthermore, the instability onset of monocoque shells exhibits a pronounced imperfection sensitivity. The vibration correlation technique (VCT) is being developed as a nondestructive test method for evaluation of the buckling load of the shells. In this study, accuracy and robustness of an existing and a modified VCT method are evaluated. With this aim, more than 20 thin-walled unstiffened CFRP shells have been produced and tested. The results obtained suggest that the vibration response under loads exceeding 0.25 of the linear buckling load needs to be characterized for a successful application of the VCT. Then the largest unconservative discrepancy of prediction by the modified VCT method amounted to ca. 22% of the critical load. Applying loads exceeding 0.9 of the buckling load reduced the average relative discrepancy to 6.4%. Full article
(This article belongs to the Special Issue Fiber-Reinforced Composites: Innovative Solutions and Advanced Analysis Methods)
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Figure 1

Figure 1
<p>Application of vibration correlation technique (VCT) [<a href="#B23-polymers-12-03069" class="html-bibr">23</a>] to monocoque shells: (<b>a</b>) Parity plot of VCT-predicted vs. experimental knock-down factors (KDFs); (<b>b</b>) VCT-predicted KDF as a function of the relative length parameter of shell (the dashed lines indicate the composite shell geometries considered in the present study).</p> Full article ">Figure 2
<p>Schematic of the setup for compression tests of composite cylinders: (<b>a</b>) Testing by means parallel loading plates; (<b>b</b>) Testing using a hemispherical joint.</p> Full article ">Figure 3
<p>Schematic of the mounting of composite cylinders: (<b>a</b>) In the groove of a steel ring; (<b>b</b>) Potting onto plates of the test machine. Dimensions in the figure are in mm.</p> Full article ">Figure 4
<p>Test setup for characterization of the vibration response of a carbon fiber-reinforced polymer (CFRP) cylinder: (<b>a</b>) Overview of the experimental setup with a specimen installed between loading plates; (<b>b</b>) Placement of the loudspeaker for excitation of vibrations.</p> Full article ">Figure 5
<p>Load–shortening diagrams of cylinders with dimensions: (<b>a</b>) D = 100 mm and H = 200 mm; (<b>b</b>) D = 100 mm and H = 400 mm; (<b>c</b>) D = 300 mm and H = 150; (<b>d</b>) D = 300 mm and H = 300. Results of tests employing a hemispherical joint are plotted by dashed lines, for parallel plates—by solid lines.</p> Full article ">Figure 6
<p>Buckling modes of cylinders with the following dimensions: (<b>a</b>) D = 100 mm and H = 200 mm; (<b>b</b>) D = 100 mm and H = 400 mm; (<b>c</b>) D = 300 mm and H = 150; (<b>d</b>) D = 300 mm and H = 300.</p> Full article ">Figure 7
<p>Typical natural frequency spectra of unloaded cylinders of dimensions: (<b>a</b>) D = 100 mm and H = 200 mm; (<b>b</b>) D = 100 mm and H = 400 mm; (<b>c</b>) D = 300 mm and H = 150; (<b>d</b>) D = 300 mm and H = 300.</p> Full article ">Figure 8
<p>Mode shapes corresponding to the first natural frequency of unloaded cylinders of dimensions: (<b>a</b>) D = 100 mm and H = 200 mm; (<b>b</b>) D = 100 mm and H = 400 mm; (<b>c</b>) D = 300 mm and H = 150; (<b>d</b>) D = 300 mm and H = 300.</p> Full article ">Figure 9
<p>Reduction of the natural frequency due to the axial compression for cylinders of dimensions: (<b>a</b>) D = 100 mm and H = 200 mm; (<b>b</b>) D = 100 mm and H = 400 mm; (<b>c</b>) D = 300 mm and H = 150; (<b>d</b>) D = 300 mm and H = 300. The results of tests employing a hemispherical joint are plotted by the dashed lines, and for parallel plates—by the solid lines.</p> Full article ">Figure 10
<p>Ratio of VCT-estimated and experimental buckling loads, <span class="html-italic">P</span><sub>VCT</sub>/<span class="html-italic">P</span><sub>b</sub>, for method M2 as a function of that for method M1, using the maximum load <span class="html-italic">P</span>/<span class="html-italic">P</span><sub>b</sub> ≥ 0.87 in vibration tests.</p> Full article ">Figure 11
<p>VCT-predicted knock-down factor, using maximum load in vibration tests <span class="html-italic">P</span>/<span class="html-italic">P</span><sub>b</sub> ≥ 0.87, as a function of the experimental KDF for VCT method: (<b>a</b>) M1; (<b>b</b>) M2.</p> Full article ">Figure 12
<p>Predicted buckling load <span class="html-italic">P</span><sub>VCT</sub>/<span class="html-italic">P</span><sub>b</sub> as a function of the highest axial load used in vibration tests, <span class="html-italic">P</span>/<span class="html-italic">P</span><sub>cr</sub>, for <span class="html-italic">P</span>/<span class="html-italic">P</span><sub>cr</sub> &gt; 0.25, using the VCT method: (<b>a</b>) M1; (<b>b</b>) M2.</p> Full article ">
13 pages, 1886 KiB  
Article
Structural and Dynamical Characteristics of Short-Chain Branched Ring Polymer Melts at Interface under Shear Flow
by Seung Heum Jeong, Soowon Cho, Tae Yong Ha, Eun Jung Roh and Chunggi Baig
Polymers 2020, 12(12), 3068; https://doi.org/10.3390/polym12123068 - 21 Dec 2020
Cited by 9 | Viewed by 2733
Abstract
We present a detailed analysis of the interfacial chain structure and dynamics of confined polymer melt systems under shear over a wide range of flow strengths using atomistic nonequilibrium molecular dynamics simulations, paying particular attention to the rheological influence of the closed-loop ring [...] Read more.
We present a detailed analysis of the interfacial chain structure and dynamics of confined polymer melt systems under shear over a wide range of flow strengths using atomistic nonequilibrium molecular dynamics simulations, paying particular attention to the rheological influence of the closed-loop ring geometry and short-chain branching. We analyzed the interfacial slip, characteristic molecular mechanisms, and deformed chain conformations in response to the applied flow for linear, ring, short-chain branched (SCB) linear, and SCB ring polyethylene melts. The ring topology generally enlarges the interfacial chain dimension along the neutral direction, enhancing the dynamic friction of interfacial chains moving against the wall in the flow direction. This leads to a relatively smaller degree of slip (ds) for the ring-shaped polymers compared with their linear analogues. Furthermore, short-chain branching generally resulted in more compact and less deformed chain structures via the intrinsically fast random motions of the short branches. The short branches tend to be oriented more perpendicular (i.e., aligned in the neutral direction) than parallel to the backbone, which is mostly aligned in the flow direction, thereby enhancing the dynamic wall friction of the moving interfacial chains toward the flow direction. These features afford a relatively lower ds and less variation in ds in the weak-to-intermediate flow regimes. Accordingly, the interfacial SCB ring system displayed the lowest ds among the studied polymer systems throughout these regimes owing to the synergetic effects of ring geometry and short-chain branching. On the contrary, the structural disturbance exerted by the highly mobile short branches promotes the detachment of interfacial chains from the wall at strong flow fields, which results in steeper increasing behavior of the interfacial slip for the SCB polymers in the strong flow regime compared to the pure linear and ring polymers. Full article
(This article belongs to the Special Issue Theory of Polymers at Interfaces)
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Figure 1

Figure 1
<p>Degree of slip (<math display="inline"><semantics> <mrow> <msub> <mi>d</mi> <mi>s</mi> </msub> </mrow> </semantics></math>) as a function of the reduced shear rate <math display="inline"><semantics> <mrow> <msup> <mover accent="true"> <mi>γ</mi> <mo>˙</mo> </mover> <mo>*</mo> </msup> <mo>≡</mo> <mover accent="true"> <mi>γ</mi> <mo>˙</mo> </mover> <msqrt> <mrow> <mrow> <mrow> <mi>m</mi> <msup> <mi>σ</mi> <mn>2</mn> </msup> </mrow> <mo>/</mo> <mi>ε</mi> </mrow> </mrow> </msqrt> </mrow> </semantics></math> for the simulated C<sub>128</sub>H<sub>258</sub> linear (Linear; black triangles), C<sub>128</sub>H<sub>256</sub> ring (Ring; black circles), C<sub>178</sub>H<sub>358</sub> SCB linear (SCB_L; orange triangles), and C<sub>178</sub>H<sub>356</sub> SCB ring (SCB_R; orange circles) PE melt systems. The vertical black dashed lines (Linear), black dash-dotted lines (Ring), and orange dashed line (SCB_L and SCB_R) separate the characteristic flow regimes with respect to <span class="html-italic">d</span><sub>s</sub> for each system. It is noted that while the linear and ring polymers exhibit three distinct characteristic <span class="html-italic">d</span><sub>s</sub> regimes (increasing, decreasing, and increasing) as a function of shear rate, the SCB systems show almost constant behavior of <math display="inline"><semantics> <mrow> <msub> <mi>d</mi> <mi>s</mi> </msub> </mrow> </semantics></math> in the weak and intermediate flow regimes and increasing behavior of <span class="html-italic">d</span><sub>s</sub> in the strong flow regime. The error bars are smaller than the size of the symbols unless otherwise indicated.</p> Full article ">Figure 2
<p>Schematic description of the characteristic molecular mechanisms for the interfacial linear, ring, SCB linear, and SCB ring polymers in the three representative (weak, intermediate, and strong) flow regimes. These mechanisms underlie the general behavior of the interfacial slip (<math display="inline"><semantics> <mrow> <msub> <mi>d</mi> <mi>s</mi> </msub> </mrow> </semantics></math>) for each system. <math display="inline"><semantics> <mrow> <msub> <mi>ξ</mi> <mi>w</mi> </msub> </mrow> </semantics></math> denotes the polymer-wall friction coefficient.</p> Full article ">Figure 3
<p>Streaming velocity profiles (normalized by the applied wall velocity <math display="inline"><semantics> <mrow> <msub> <mi>V</mi> <mi>w</mi> </msub> </mrow> </semantics></math>) along the velocity gradient direction at a certain intermediate shear rate for the simulated C<sub>128</sub>H<sub>258</sub> linear (black triangles), C<sub>128</sub>H<sub>256</sub> ring (black circles), C<sub>178</sub>H<sub>358</sub> SCB linear (orange triangles), and C<sub>178</sub>H<sub>356</sub> SCB ring (orange circles) PE melts. The solid line represents the ideal streaming velocity profile assuming the no-slip boundary condition.</p> Full article ">Figure 4
<p>The <span class="html-italic">xx</span>-, <span class="html-italic">yy</span>-, and <span class="html-italic">zz</span>-components of the gyration tensor <b>G</b> (<math display="inline"><semantics> <mrow> <msub> <mi>G</mi> <mrow> <mi>α</mi> <mi>β</mi> </mrow> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mi>N</mi> </mfrac> <mstyle displaystyle="true"> <munderover> <mo>∑</mo> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>N</mi> </munderover> <mrow> <mo stretchy="false">(</mo> <msubsup> <mi>r</mi> <mrow> <mi>i</mi> <mo>,</mo> <mi>α</mi> </mrow> <mrow/> </msubsup> <mo>−</mo> <msubsup> <mi>r</mi> <mrow> <mi>c</mi> <mo>,</mo> <mi>α</mi> </mrow> <mrow/> </msubsup> <mo stretchy="false">)</mo> <mo stretchy="false">(</mo> <msubsup> <mi>r</mi> <mrow> <mi>i</mi> <mo>,</mo> <mi>β</mi> </mrow> <mrow/> </msubsup> <mo>−</mo> <msubsup> <mi>r</mi> <mrow> <mi>c</mi> <mo>,</mo> <mi>β</mi> </mrow> <mrow/> </msubsup> <mo stretchy="false">)</mo> </mrow> </mstyle> </mrow> </semantics></math>, where <math display="inline"><semantics> <mrow> <msubsup> <mi mathvariant="bold">r</mi> <mi mathvariant="normal">i</mi> <mrow/> </msubsup> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msubsup> <mi mathvariant="bold">r</mi> <mi mathvariant="normal">c</mi> <mrow/> </msubsup> </mrow> </semantics></math> denote the position vectors of atom <span class="html-italic">i</span> and the chain center-of-mass with α, β = <span class="html-italic">x</span>, <span class="html-italic">y</span>, <span class="html-italic">z</span>) for the interfacial chains whose center-of-mass is located within a distance of 2.5 σ from the wall for the (<b>a</b>) C<sub>128</sub>H<sub>258</sub> linear (black triangles) and C<sub>178</sub>H<sub>358</sub> SCB linear (orange triangles) and (<b>b</b>) C<sub>128</sub>H<sub>256</sub> ring (black circles) and C<sub>178</sub>H<sub>356</sub> SCB ring (orange circles) systems as a function of the applied shear rate. To allow comparison with the pure ring and linear systems, only the chain backbone, excluding the short branches, was considered in the calculation of <span class="html-italic">G</span> for the SCB systems. The symbols and vertical lines have the same meaning as in <a href="#polymers-12-03068-f001" class="html-fig">Figure 1</a>. The error bars are smaller than the size of the symbols unless otherwise indicated.</p> Full article ">Figure 5
<p>(<b>a</b>) Schematic depiction of the proposed Brightness analysis for a ring-shaped polymer chain. (<b>b</b>) Probability distribution functions (PDFs) resulting from the Brightness analysis applied to the interfacial chains for the pure ring (left panel) and SCB ring (right panel) polymers at a relatively high shear rate (<math display="inline"><semantics> <mrow> <msup> <mover accent="true"> <mi>γ</mi> <mo>˙</mo> </mover> <mo>*</mo> </msup> </mrow> </semantics></math> = 0.02). Note that the molecular configurations for each part of the ring backbone are categorized into six representative classes (stretched, coil, dumbbell, kink, half-dumbbell, and fold).</p> Full article ">Figure 6
<p>(<b>a</b>) Schematic depiction of the two types of loop tumbling mechanisms (end-loop tumbling and center-loop tumbling) of the interfacial ring chains. (<b>b</b>) Proportion of end-loop tumbling (triangles) and center-loop tumbling (squares) of the interfacial chains as a function of the shear rate for the pure ring (black symbols) and SCB ring (orange symbols) polymers. The vertical lines have the same meaning as in <a href="#polymers-12-03068-f001" class="html-fig">Figure 1</a>.</p> Full article ">
30 pages, 5422 KiB  
Review
Insight into the Structure and Dynamics of Polymers by Neutron Scattering Combined with Atomistic Molecular Dynamics Simulations
by Arantxa Arbe, Fernando Alvarez and Juan Colmenero
Polymers 2020, 12(12), 3067; https://doi.org/10.3390/polym12123067 - 21 Dec 2020
Cited by 18 | Viewed by 4026
Abstract
Combining neutron scattering and fully atomistic molecular dynamics simulations allows unraveling structural and dynamical features of polymer melts at different length scales, mainly in the intermolecular and monomeric range. Here we present the methodology developed by us and the results of its application [...] Read more.
Combining neutron scattering and fully atomistic molecular dynamics simulations allows unraveling structural and dynamical features of polymer melts at different length scales, mainly in the intermolecular and monomeric range. Here we present the methodology developed by us and the results of its application during the last years in a variety of polymers. This methodology is based on two pillars: (i) both techniques cover approximately the same length and time scales and (ii) the classical van Hove formalism allows easily calculating the magnitudes measured by neutron scattering from the simulated atomic trajectories. By direct comparison with experimental results, the simulated cell is validated. Thereafter, the information of the simulations can be exploited, calculating magnitudes that are experimentally inaccessible or extending the parameters range beyond the experimental capabilities. We show how detailed microscopic insight on structural features and dynamical processes of various kinds has been gained in polymeric systems with different degrees of complexity, and how intriguing questions as the collective behavior at intermediate length scales have been faced. Full article
(This article belongs to the Special Issue State-of-the-Art Polymer Science and Technology in Spain (2020,2021))
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Cartoon illustrating the relevant structural features of polymers as function of the length scale of observation and magnitudes accessed in neutron diffraction experiments: the single chain structure factor on labelled samples at low scattering angles (<b>left</b>) and the structure factor on fully deuterated samples (<b>right</b>).</p> Full article ">Figure 2
<p>Illustration of the magnitudes in a scattering experiment and scheme of the functions involved in the different domians in the van Hove formalism of neutron scattering.</p> Full article ">Figure 3
<p>Block-diagram of the strategy followed for combining NS and MD-simulations.</p> Full article ">Figure 4
<p>Ratio between coherent and incoherent differential cross sections measured with diffraction with PA (points) and calculated from the MD-simulations (lines) on PMMA with deuterated ester methyl group (PMMA-d3e) (<b>a</b>) and PMMA with deuterated <math display="inline"><semantics> <mi>α</mi> </semantics></math>-methyl group and main chain (PMMA-d5) (<b>b</b>). The respective coherent cross sections calculated from the simulations with the different molecular group correlations, properly weighted by the corresponding neutron scattering lengths, are shown in panels (<b>c</b>,<b>d</b>). Adapted with permission from [<a href="#B57-polymers-12-03067" class="html-bibr">57</a>]. Copyright (2006) American Chemical Society.</p> Full article ">Figure 5
<p>(<b>a</b>) Radial probability distribution function calculated at 200 K (<math display="inline"><semantics> <msub> <mi>T</mi> <mi>g</mi> </msub> </semantics></math> + 20 K) and <span class="html-italic">t</span> = 1 ns for the different kinds of hydrogens in the 1,4-units of PB. The upper panel displays the schematic representation of the isomeric forms of 1,4-PB monomers and shows with colors the nomenclature for the different types of hydrogens. (<b>b</b>) Radial probability distribution function calculated for <math display="inline"><semantics> <msup> <mrow/> <mn>1</mn> </msup> </semantics></math>H<math display="inline"><semantics> <msub> <mrow/> <mi>t</mi> </msub> </semantics></math> (methyne hydrogen in the trans unit) at the same temperature at the different times indicated. For clarity the origins are shifted to the levels displayed by the horizontal dotted lines. The solid lines show the description obtained by the model proposed in Refs. [<a href="#B75-polymers-12-03067" class="html-bibr">75</a>,<a href="#B76-polymers-12-03067" class="html-bibr">76</a>].</p> Full article ">Figure 6
<p>(<b>a</b>) Master curve giving the <span class="html-italic">Q</span>-dependence of <math display="inline"><semantics> <msub> <mi>τ</mi> <mi>w</mi> </msub> </semantics></math> constructed with results from different polymers (see legend; PH:phenoxy), applying polymer-dependent normalizing factors (<math display="inline"><semantics> <msub> <mi>τ</mi> <mi>p</mi> </msub> </semantics></math>). The solid line is the Gaussian behavior. (<b>b</b>) Master curve built combining NS from different spectrometers and MD-simulations results for PId3 [<a href="#B85-polymers-12-03067" class="html-bibr">85</a>,<a href="#B86-polymers-12-03067" class="html-bibr">86</a>], applying <span class="html-italic">T</span>-dependent shift factors <math display="inline"><semantics> <msub> <mi>a</mi> <mi>T</mi> </msub> </semantics></math>. The solid line is the description by the anomalous jump diffusion model with the distribution of jump lengths in the inset. Adapted from [<a href="#B6-polymers-12-03067" class="html-bibr">6</a>] with permission from The Royal Society of Chemistry.</p> Full article ">Figure 7
<p>Comparison of the NSE results on a fully deuterated PIB sample [<a href="#B99-polymers-12-03067" class="html-bibr">99</a>] (symbols) and calculated from simulations [<a href="#B65-polymers-12-03067" class="html-bibr">65</a>] (solid lines) at 390 K (<b>a</b>) and 335 K (<b>b</b>) at the <span class="html-italic">Q</span>-values indicated in (<b>a</b>). Inset in (<b>b</b>) <span class="html-italic">Q</span>-dependence of the apparent activation energy for collective relaxation obtained from KWW fits of the experimental (solid) and simulated (empty) data. Examples of the fits are shown for <math display="inline"><semantics> <mrow> <mi>Q</mi> <mo>≈</mo> <msub> <mi>Q</mi> <mrow> <mi>m</mi> <mi>a</mi> <mi>x</mi> </mrow> </msub> </mrow> </semantics></math>. Adapted with permission from [<a href="#B65-polymers-12-03067" class="html-bibr">65</a>]. Copyright (2014) American Chemical Society.</p> Full article ">Figure 8
<p>Normalized partial dynamic structure factors of deuterated PMMA corresponding to the different atomic groups considered [see the insert in (a) for the color code]. The total dynamic structure factor is shown in black. The lines are KWW descriptions for <math display="inline"><semantics> <mrow> <mi>t</mi> <mspace width="3.33333pt"/> <mo>≥</mo> <mspace width="3.33333pt"/> </mrow> </semantics></math>4 ps. (<b>a</b>) <math display="inline"><semantics> <mrow> <mi>Q</mi> <mspace width="3.33333pt"/> <mo>=</mo> <mspace width="3.33333pt"/> <mn>0.8</mn> <mspace width="3.33333pt"/> <msup> <mrow> <mo>Å</mo> </mrow> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </mrow> </semantics></math> (first structure factor peak); (<b>b</b>) <math display="inline"><semantics> <mrow> <mi>Q</mi> <mspace width="3.33333pt"/> <mo>=</mo> <mspace width="3.33333pt"/> <mn>1.9</mn> <mspace width="3.33333pt"/> <msup> <mrow> <mo>Å</mo> </mrow> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </mrow> </semantics></math> (second structure factor peak). Adapted with permission from [<a href="#B70-polymers-12-03067" class="html-bibr">70</a>]. Copyright (2006) American Chemical Society.</p> Full article ">Figure 9
<p>(<b>a</b>) Normalized Rouse correlators calculated for PEP at <math display="inline"><semantics> <msub> <mi>T</mi> <mi>g</mi> </msub> </semantics></math> + 280 K and the mode-numbers indicated. Lines are fits with stretched exponentials. The obtained stretching parameters and effective friction coefficients (after ARS corrections) are displayed in (<b>b</b>). Rouse behavior corresponds to <math display="inline"><semantics> <mi>β</mi> </semantics></math> = 1 and mode-independent friction (solid line). Adapted with permission from [<a href="#B119-polymers-12-03067" class="html-bibr">119</a>]. Copyright (2011) American Chemical Society.</p> Full article ">Figure 10
<p>(<b>a</b>) Direct comparison of the ratio between coherent and incoherent differential cross sections measured at 300 K and calculated from the simulations at 360 K for fully deuterated PAO with <math display="inline"><semantics> <msub> <mi>n</mi> <mi>C</mi> </msub> </semantics></math> = 4. (<b>b</b>) Contributions to the normalized total structure factors for this polymer calculated from the MD-simulations. This panel shows a slice of the simulation cell. Main-chain atoms are represented in blue, side-group atoms in red. The nano-segregation can be appreciated at first sight. The definitions of MC and SG subsystems are shown in the scheme of the monomer in (<b>a</b>) by the green and orange rectangles respectively. Adapted with permission from [<a href="#B150-polymers-12-03067" class="html-bibr">150</a>]. Copyright (2012) American Chemical Society.</p> Full article ">Figure 11
<p><span class="html-italic">Q</span>-dependence of the average characteristic time for collective (empty squares) and self-correlation (circles) functions of PIB obtained from simulations. Filled squares are the experimental collective times [<a href="#B99-polymers-12-03067" class="html-bibr">99</a>]. Solid line: description of the self-correlation times by the anomalous jump diffusion model. Dashed-dotted line: description of the collective times by the proposed model [<a href="#B65-polymers-12-03067" class="html-bibr">65</a>,<a href="#B155-polymers-12-03067" class="html-bibr">155</a>,<a href="#B156-polymers-12-03067" class="html-bibr">156</a>]. The dotted line represents the diffusive contribution and the dashed line the <math display="inline"><semantics> <mrow> <mi>Q</mi> <mo stretchy="false">→</mo> <mn>0</mn> </mrow> </semantics></math> contribution, with the location of the non-diffusive time indicated by the horizontal line. Adapted with permission from [<a href="#B65-polymers-12-03067" class="html-bibr">65</a>]. Copyright (2014) American Chemical Society.</p> Full article ">Figure 12
<p>(<b>a</b>) Comparison of the coherent and incoherent dynamical structure factors measured by LET on D<math display="inline"><semantics> <msub> <mrow/> <mn>2</mn> </msub> </semantics></math>O at 295 K at <math display="inline"><semantics> <mrow> <mi>Q</mi> <mspace width="3.33333pt"/> <mo>=</mo> <mspace width="3.33333pt"/> <mn>0.52</mn> <mspace width="3.33333pt"/> <msup> <mrow> <mo>Å</mo> </mrow> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> </mrow> </semantics></math> [<a href="#B19-polymers-12-03067" class="html-bibr">19</a>]. Vertical dotted lines represent the resolution FWHM. (<b>b</b>) <span class="html-italic">Q</span>-dependence of the characteristic relaxation times: <math display="inline"><semantics> <msub> <mi>τ</mi> <mi>d</mi> </msub> </semantics></math> (circles) and <math display="inline"><semantics> <msub> <mi>τ</mi> <mi>c</mi> </msub> </semantics></math> (squares; from MD-simulations, squares with crosses). The <math display="inline"><semantics> <msub> <mi>τ</mi> <mi>d</mi> </msub> </semantics></math> values have been obtained from incoherent scattering (<math display="inline"><semantics> <msubsup> <mi>τ</mi> <mi>d</mi> <mrow> <mi>i</mi> <mi>n</mi> <mi>c</mi> </mrow> </msubsup> </semantics></math>) and from the fit of the coherent scattering results to the model (•). Solid line: fit of <math display="inline"><semantics> <mrow> <msup> <mi>D</mi> <mrow> <mo>−</mo> <mn>1</mn> </mrow> </msup> <msup> <mi>Q</mi> <mrow> <mo>−</mo> <mn>2</mn> </mrow> </msup> </mrow> </semantics></math> to <math display="inline"><semantics> <msubsup> <mi>τ</mi> <mi>d</mi> <mrow> <mi>i</mi> <mi>n</mi> <mi>c</mi> </mrow> </msubsup> </semantics></math>. <math display="inline"><semantics> <msub> <mi>τ</mi> <mi>c</mi> </msub> </semantics></math> and <math display="inline"><semantics> <mrow> <mo stretchy="false">〈</mo> <mi>τ</mi> <mo stretchy="false">〉</mo> </mrow> </semantics></math>-values calculated with the model are shown by the dashed and dashed-dotted lines respectively. The temperature is 295 K [<a href="#B19-polymers-12-03067" class="html-bibr">19</a>]. Inset: Ratio between coherent and incoherent differential cross sections of D<math display="inline"><semantics> <msub> <mrow/> <mn>2</mn> </msub> </semantics></math>O at 298 K (hollow dots) as function of <span class="html-italic">Q</span> and calculated from MD-simulations (solid line). Adapted from [<a href="#B19-polymers-12-03067" class="html-bibr">19</a>].</p> Full article ">
18 pages, 3199 KiB  
Article
New Functionalized Polymeric Sensor Based NiO/MgO Nanocomposite for Potentiometric Determination of Doxorubicin Hydrochloride in Commercial Injections and Human Plasma
by Nawal A. Alarfaj and Maha F. El-Tohamy
Polymers 2020, 12(12), 3066; https://doi.org/10.3390/polym12123066 - 21 Dec 2020
Cited by 18 | Viewed by 2984
Abstract
The ultra-functional potential of nickel oxide (NiO) and magnesium oxide (MgO) nanoparticles (NPs), provides for extensive attention in the use of these metal oxides as a remarkable and electroactive nanocomposite in potentiometric and sensing investigations. This work proposed a new strategy for quantifying [...] Read more.
The ultra-functional potential of nickel oxide (NiO) and magnesium oxide (MgO) nanoparticles (NPs), provides for extensive attention in the use of these metal oxides as a remarkable and electroactive nanocomposite in potentiometric and sensing investigations. This work proposed a new strategy for quantifying doxorubicin hydrochloride (DOX) in pharmaceuticals and human plasma by preparing a NiO/MgO core-shell nanocomposite modified coated wire membrane sensor. Doxorubicin hydrochloride was incorporated with phosphomolybdic acid (PMA) to produce doxorubicin hydrochloride phosphomolybdate (DOX-PM) as an electroactive material in the presence of polymeric high molecular weight poly vinyl chloride (PVC) and solvent mediator o-nitrophenyloctyl ether (o-NPOE). The modified sensor exhibited ultra sensitivity and high selectivity for the detection and quantification of doxorubicin hydrochloride with a linear relationship in the range of 1.0 × 10−11–1.0 × 10−2 mol L−1. The equation of regression was estimated to be EmV = (57.86 ± 0.8) log [DOX] + 723.19. However, the conventional type DOX-PM showed a potential response over a concentration range of 1.0 × 10−6–1.0 × 10−2 mol L−1 and a regression equation of EmV = (52.92 ± 0.5) log [DOX] + 453.42. The suggested sensors were successfully used in the determination of doxorubicin hydrochloride in commercial injections and human plasma. Full article
(This article belongs to the Special Issue High-Performance Polymeric Sensors )
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<p>Schematic steps for the reparation of magnesium oxide nanoparticles (MgONPs) and NiO/MgO nanocomposite.</p> Full article ">Figure 2
<p>Schematic diagram for the preparation of the modified coated wire membrane sensor and the potentiometric system.</p> Full article ">Figure 3
<p>UV-Vis spectrum of the synthesized NiO/MgO nanocomposite with respect to MgONPs and NiONPs at an absorbance of 200–500 nm.</p> Full article ">Figure 4
<p>Fourier-Transform Infrared (FT-IR) spectra of the synthesized (<b>c</b>) NiO/MgO nanocomposite with respect to (<b>a</b>) NiONPs and (<b>b</b>) MgONPs at a wavenumber range from 4400 to 400 cm<sup>−1.</sup></p> Full article ">Figure 5
<p>(<b>a</b>–<b>c</b>) Energy-Dispersive X-Ray Spectroscopy (EDX) and (<b>d</b>–<b>f</b>) X-Ray Diffraction (XRD) spectra of NiONPs, MgONPs, and NiO/MgO nanocomposite.</p> Full article ">Figure 6
<p>Transmission electron microscope (TEM) images of (<b>a</b>) NiONPs, (<b>b</b>) MgONPs, and (<b>c</b>) NiO/MgO nanocomposite at magnification 200,000×.</p> Full article ">Figure 7
<p>Scanning electron microscope (SEM) images of (<b>a</b>) NiONPs, (<b>b</b>) MgONPs, and (<b>c</b>) NiO/MgONPs.</p> Full article ">Figure 8
<p>Calibration graphs of the fabricated (<b>a</b>) Conventional DOX-PM and (<b>b</b>) Modified DOX-PM-NiO/MgO nanocomposite coated wire sensors.</p> Full article ">Figure 9
<p>Effect of pH on the fabricated conventional DOX-PM and modified DOX-PM-NiO/MgO nanocomposite coated wire sensors using 1.0 × 10<sup>−4</sup> mol L<sup>−1</sup> of DOX solution.</p> Full article ">
14 pages, 8947 KiB  
Article
Chitosan–Hydroxyapatite Composite Layers Generated in Radio Frequency Magnetron Sputtering Discharge: From Plasma to Structural and Morphological Analysis of Layers
by Dragana Biliana Dreghici, Bogdan Butoi, Daniela Predoi, Simona Liliana Iconaru, Ovidiu Stoican and Andreea Groza
Polymers 2020, 12(12), 3065; https://doi.org/10.3390/polym12123065 - 21 Dec 2020
Cited by 18 | Viewed by 3342
Abstract
Chitosan–hydroxyapatite composite layers were deposited on Si substrates in radio frequency magnetron sputtering discharges. The plasma parameters calculated from the current–voltage radio frequency-compensated Langmuir probe characteristics indicate a huge difference between the electron temperature in the plasma and at the sample holder. These [...] Read more.
Chitosan–hydroxyapatite composite layers were deposited on Si substrates in radio frequency magnetron sputtering discharges. The plasma parameters calculated from the current–voltage radio frequency-compensated Langmuir probe characteristics indicate a huge difference between the electron temperature in the plasma and at the sample holder. These findings aid in the understanding of the coagulation pattern of hydroxyapatite–chitosan macromolecules on the substrate surface. An increase in the sizes of the spherical-shape grain-like structures formed on the coating surface with the plasma electron number density was observed. The link between the chemical composition of the chitosan–hydroxyapatite composite film and the species sputtered from the target or produced by excitation/ionization mechanisms in the plasma was determined on the basis of X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and residual gas mass spectrometry analysis. Full article
(This article belongs to the Special Issue Advances in Polymer Based Composite Coatings)
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<p>Dependence of electron energy distribution function on applied radio frequency (rf) power for: (<b>a</b>) <span class="html-italic">p</span> = 2 × 10<sup>−3</sup> mbarr; (<b>b</b>) <span class="html-italic">p</span> = 5 × 10<sup>−3</sup> mbarr; (<b>c</b>) <span class="html-italic">p</span> = 1.2 × 10<sup>−2</sup> mbarr.</p> Full article ">Figure 2
<p>Mass spectrum of the residual gas extracted from the vacuum chamber during plasma on (black line) and plasma off (red line).</p> Full article ">Figure 3
<p>XPS data of HApCs coatings deposited on Si substrates at 5 × 10<sup>−3</sup> mbarr Ar gas working pressure: (<b>a</b>) survey spectrum; (<b>b</b>) Ca 2p; (<b>c</b>) P 2p; (<b>d</b>) O 1s; (<b>e</b>) C1s; and (<b>f</b>) N 1s high-resolution lines.</p> Full article ">Figure 4
<p>FTIR spectra of: (<b>a</b>) HApCs target; (<b>b</b>) HApCs coating deposited on Si substrate at 5 × 10<sup>−3</sup> mbarr Ar gas working pressure; FTIR deconvoluted spectra of HApCs target and of HApCs coating deposited on Si substrate at 5 × 10<sup>−3</sup> mbarr Ar gas working pressure in: (<b>c</b>,<b>e</b>) 1200–850 cm<sup>−1</sup> range; (<b>d</b>,<b>f</b>) 680–500 cm<sup>−1</sup> range.</p> Full article ">Figure 4 Cont.
<p>FTIR spectra of: (<b>a</b>) HApCs target; (<b>b</b>) HApCs coating deposited on Si substrate at 5 × 10<sup>−3</sup> mbarr Ar gas working pressure; FTIR deconvoluted spectra of HApCs target and of HApCs coating deposited on Si substrate at 5 × 10<sup>−3</sup> mbarr Ar gas working pressure in: (<b>c</b>,<b>e</b>) 1200–850 cm<sup>−1</sup> range; (<b>d</b>,<b>f</b>) 680–500 cm<sup>−1</sup> range.</p> Full article ">Figure 5
<p>(<b>a</b>) Survey SEM image of HApCs coatings generated at 5 × 10<sup>−3</sup> mbarr Ar gas working pressure; (<b>b</b>) 3D image of <a href="#polymers-12-03065-f001" class="html-fig">Figure 1</a> performed with ImageJ software; (<b>c</b>) histogram of particle sizes.</p> Full article ">Figure 6
<p>SEM images of HApCs coatings at: (<b>a</b>) p = 2 × 10<sup>−3</sup> mbarr; (<b>c</b>) p = 5 × 10<sup>−3</sup> mbarr; (<b>e</b>) p = 1.2 × 10<sup>−2</sup> mbarr; 3D images of: (<b>b</b>) Figure 6a; (<b>d</b>) Figure 6c; (<b>f</b>) Figure 6e; performed with ImageJ software.</p> Full article ">Figure 7
<p>EDS spectrum of HApCs layers generated at 5 × 10<sup>−3</sup> mbarr Ar gas working pressure.</p> Full article ">Figure 8
<p>2D SEM-EDS elemental mapping of the HApCs coating.</p> Full article ">
13 pages, 5249 KiB  
Article
Effect of Microcapsule Content on Diels-Alder Room Temperature Self-Healing Thermosets
by Sadella C. Santos, John J. La Scala and Giuseppe R. Palmese
Polymers 2020, 12(12), 3064; https://doi.org/10.3390/polym12123064 - 21 Dec 2020
Cited by 3 | Viewed by 2075
Abstract
A furan functionalized epoxy-amine thermoset with an embedded microcapsule healing system that utilizes reversible Diels-Alder healing chemistry was used to investigate the influence of microcapsule loading on healing efficiency. A urea-formaldehyde encapsulation technique was used to create capsules with an average diameter of [...] Read more.
A furan functionalized epoxy-amine thermoset with an embedded microcapsule healing system that utilizes reversible Diels-Alder healing chemistry was used to investigate the influence of microcapsule loading on healing efficiency. A urea-formaldehyde encapsulation technique was used to create capsules with an average diameter of 150 µm that were filled with a reactive solution of bismaleimide in phenyl acetate. It was found that optimum healing of the thermoset occurred at 10 wt% microcapsule content for the compositions investigated. The diffusion of solvent through the crack interface and within fractured samples was investigated using analytical diffusion models. The decrease in healing efficiency at higher microcapsule loading was attributed partially to solvent-induced plasticization at the interface. The diffusion analysis also showed that the 10% optimum microcapsule concentration occurs for systems with the same interfacial solvent concentration. This suggests that additional physical and chemical phenomena are also responsible for the observed optimum. Such phenomena could include a reduction in surface area available for healing and the saturation of interfacial furan moieties by reaction with increasing amounts of maleimide. Both would result from increased microcapsule loading. Full article
(This article belongs to the Special Issue Recent Advances in Self-Healing Polymers)
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<p>Diels-Alder reaction between furan and maleimide.</p> Full article ">Figure 2
<p>SEM Images of (<b>a</b>) dried microcapsules and (<b>b</b>) crack interface of resin with 20 wt% microcapsule content. Samples were sputter coated with platinum.</p> Full article ">Figure 3
<p>Size distribution of microcapsules filled with PA and MMI-2 healing agent.</p> Full article ">Figure 4
<p>Thermogravimetric analysis (TGA) of microcapsules filled with MMI2/PA. Microcapsules used in TGA have diameters of 200 μm and less. Capsule specimens were heated at a rate of 5 °C min [<a href="#B1-polymers-12-03064" class="html-bibr">1</a>] to 100 °C and held for 30 min to stimulate water loss. This was followed by heating to 180 °C for 30 min and 200 °C for 60 min, which bracketed the boiling point of PA (b.p. 196 °C).</p> Full article ">Figure 5
<p>Maleimide concentration during reaction of furan and maleimide in 2.3 M FGE 0.26 M maleimide groups from MMI2 in PA at 25 °C.</p> Full article ">Figure 6
<p>Initial maximum load of fracture (N) of virgin fracture toughness samples (Day 0) normalized to the initial maximum load value (N) of sample of neat resin for specimen with varying microcapsule content (wt%).</p> Full article ">Figure 7
<p>Healing efficiency, η (%) vs. healing time (days) for modified fracture toughness samples with varying microcapsule content. Specimens were healed for 2, 4, 7, and 14 days.</p> Full article ">Figure 8
<p>Temperature of the extrapolated onset of the storage modulus change (°C), T<sub>onset</sub>, of DMA specimen with varying concentrations of PA in polymer (M). Data shows that with increasing mass uptake of solvent, T<sub>onset</sub> decreases.</p> Full article ">Figure 9
<p>Schematic of model for diffusion of phenyl acetate through compact tension specimen fracture surface.</p> Full article ">Figure 10
<p>Calculated concentration of PA in the polymer for samples with varying microcapsule content at varied healing times (2, 4, 7, and 14 days). The concentration at which T<sub>onset</sub> = 25 °C is also plotted.</p> Full article ">Figure 11
<p>Healing efficiency, η, vs. concentration of PA in the polymer as calculated by the analytical model for specimena with varying microcapsule content at varied healing times (2, 4, 7, and 14 days). The concentration needed for T<sub>onset</sub> = 25 °C is plotted to differentiate which specimens are affected by plasticization.</p> Full article ">
10 pages, 1700 KiB  
Article
Poly(d,l-lactide-co-glycolide) (PLGA) Nanoparticles Loaded with Proteolipid Protein (PLP)—Exploring a New Administration Route
by Alexandre Ferreira Lima, Isabel R. Amado and Liliana R. Pires
Polymers 2020, 12(12), 3063; https://doi.org/10.3390/polym12123063 - 21 Dec 2020
Cited by 23 | Viewed by 3205
Abstract
The administration of specific antigens is being explored as a mean to re-establish immunological tolerance, namely in the context of multiple sclerosis (MS). PLP139-151 is a peptide of the myelin’s most abundant protein, proteolipid protein (PLP), which has been identified as a potent [...] Read more.
The administration of specific antigens is being explored as a mean to re-establish immunological tolerance, namely in the context of multiple sclerosis (MS). PLP139-151 is a peptide of the myelin’s most abundant protein, proteolipid protein (PLP), which has been identified as a potent tolerogenic molecule in MS. This work explored the encapsulation of the peptide into poly(lactide-co-glycolide) nanoparticles and its subsequent incorporation into polymeric microneedle patches to achieve efficient delivery of the nanoparticles and the peptide into the skin, a highly immune-active organ. Different poly(d,l-lactide-co-glycolide) (PLGA) formulations were tested and found to be stable and to sustain a freeze-drying process. The presence of trehalose in the nanoparticle suspension limited the increase in nanoparticle size after freeze-drying. It was shown that rhodamine can be loaded in PLGA nanoparticles and these into poly(vinyl alcohol)–poly(vinyl pyrrolidone) microneedles, yielding fluorescently labelled structures. The incorporation of PLP into the PLGA nanoparticles resulted in nanoparticles in a size range of 200 µm and an encapsulation efficiency above 20%. The release of PLP from the nanoparticles occurred in the first hours after incubation in physiological media. When loading the nanoparticles into microneedle patches, structures were obtained with 550 µm height and 180 µm diameter. The release of PLP was detected in PLP–PLGA.H20 nanoparticles when in physiological media. Overall, the results show that this strategy can be explored to integrate a new antigen-specific therapy in the context of multiple sclerosis, providing minimally invasive administration of PLP-loaded nanoparticles into the skin. Full article
(This article belongs to the Special Issue Polymeric Carriers for Biomedical and Nanomedicine Application)
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<p>Characterization of poly(lactide-<span class="html-italic">co</span>-glycolide) (PLGA) nanoparticles by average diameter and polydispersity index (PDI) (<span class="html-italic">n</span> = 3, measured in triplicate).</p> Full article ">Figure 2
<p>Characterization of the (<b>A</b>) PLGA20 and (<b>B</b>) PLGA.H20 nanoparticles after freeze-drying with or without trehalose (<span class="html-italic">n</span> = 3, assessed in triplicate).</p> Full article ">Figure 3
<p>Characterization of PLGA–rhodamine nanoparticles. (<b>A</b>) Average diameter of PLGA20 and PLGA.H20 nanoparticles loaded with rhodamine. (<b>B</b>) Rhodamine-loading capacity of the PLGA and PLGA.H20 nanoparticles. (<b>C</b>) Fluorescence microscopy image of polymer microneedles loaded with PLGA–rhodamine nanoparticles (exposure = 10 ms).</p> Full article ">Figure 4
<p>Characterization of PLGA nanoparticles loaded with proteolipid protein (PLP). (<b>A</b>) Average diameter and polydispersity index (PDI) of nanoparticles loaded with PLP. (<span class="html-italic">n</span> = 3, in triplicate) (<b>B</b>) loading efficiency of the different nanoparticle formulations. (<span class="html-italic">n</span> = 3) (<b>C</b>) Release of the PLP peptide into physiological media, as determined by HPLC (representative experiment out of 2).</p> Full article ">Figure 5
<p>Polymer microneedles loaded with PLGA.H20 nanoparticles. (<b>A</b>,<b>B</b>) Optical microscopy images of microneedles loaded with (<b>A</b>) plain or (<b>B</b>) PLP-loaded PLGA.H20 nanoparticles. (<b>C</b>) Characterization of the prepared polymer microneedles in terms of diameter and height. (<b>D</b>) Quantification of the PLP released from the polymeric system when immersed in PBS a 37 °C, as quantified by HPLC.</p> Full article ">
12 pages, 3004 KiB  
Article
Optimization of Preparation Conditions for Side-Emitting Polymer Optical Fibers Using Response Surface Methodology
by Xianjin Hu, Kun Yang and Cheng Zhang
Polymers 2020, 12(12), 3062; https://doi.org/10.3390/polym12123062 - 21 Dec 2020
Cited by 3 | Viewed by 1904
Abstract
Polymer optical fibers (POFs) were used for preparing side-emitting polymer optical fibers (SPOFs), which were processed with acetone and n-hexane combined in selected proportions by a solvent treatment method. The effects of the volume ratio of acetone to n-hexane and treatment time on [...] Read more.
Polymer optical fibers (POFs) were used for preparing side-emitting polymer optical fibers (SPOFs), which were processed with acetone and n-hexane combined in selected proportions by a solvent treatment method. The effects of the volume ratio of acetone to n-hexane and treatment time on response variable factors were investigated. The center composite design (CCD) based response surface methodology (RSM), a quadratic model, and a two-factor interaction model were developed to relate the preparation variables of illumination intensity, breaking strength, and rigidity. According to analysis of variance (ANOVA), the factors affecting the optimization of each response factor were determined. The predicted values after process optimization were found to be highly similar to the experimental values. The optimal conditions for the preparation of SPOF were as follows: the volume ratio of acetone to hexane was 1.703, and the treatment time was 2.716 s. The three response variables of SPOF prepared under the optimal conditions were: illumination intensity 19.339 mV, breaking strength 5.707 N, and rigidity 572.013 N·mm2. Full article
(This article belongs to the Section Polymer Physics and Theory)
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<p>Device for treating POFs.</p> Full article ">Figure 2
<p>Illumination intensity test system.</p> Full article ">Figure 3
<p>Volume ratio of acetone to n-hexane and treatment time for illumination intensity (2D).</p> Full article ">Figure 4
<p>Volume ratio of acetone to n-hexane and treatment time for illumination intensity (3D).</p> Full article ">Figure 5
<p>Volume ratio of acetone to n-hexane and treatment time for breaking strength (2D).</p> Full article ">Figure 6
<p>Volume ratio of acetone to n-hexane and treatment time for breaking strength (3D).</p> Full article ">Figure 7
<p>Volume ratio of acetone to n-hexane and treatment time for rigidity (2D).</p> Full article ">Figure 8
<p>Volume ratio of acetone to n-hexane and treatment time for rigidity (3D).</p> Full article ">Figure 9
<p>SEM image of the surface and cross-sectional views of side-emitting polymer optical fiber prepared under optimal conditions (<b>a</b>) Radial image (<b>b</b>) Cross-sectional image.</p> Full article ">
26 pages, 4045 KiB  
Review
Biopolymer Coatings for Biomedical Applications
by A. Joseph Nathanael and Tae Hwan Oh
Polymers 2020, 12(12), 3061; https://doi.org/10.3390/polym12123061 - 21 Dec 2020
Cited by 89 | Viewed by 9175
Abstract
Biopolymer coatings exhibit outstanding potential in various biomedical applications, due to their flexible functionalization. In this review, we have discussed the latest developments in biopolymer coatings on various substrates and nanoparticles for improved tissue engineering and drug delivery applications, and summarized the latest [...] Read more.
Biopolymer coatings exhibit outstanding potential in various biomedical applications, due to their flexible functionalization. In this review, we have discussed the latest developments in biopolymer coatings on various substrates and nanoparticles for improved tissue engineering and drug delivery applications, and summarized the latest research advancements. Polymer coatings are used to modify surface properties to satisfy certain requirements or include additional functionalities for different biomedical applications. Additionally, polymer coatings with different inorganic ions may facilitate different functionalities, such as cell proliferation, tissue growth, repair, and delivery of biomolecules, such as growth factors, active molecules, antimicrobial agents, and drugs. This review primarily focuses on specific polymers for coating applications and different polymer coatings for increased functionalization. We aim to provide broad overview of latest developments in the various kind of biopolymer coatings for biomedical applications, in order to highlight the most important results in the literatures, and to offer a potential outline for impending progress and perspective. Some key polymer coatings were discussed in detail. Further, the use of polymer coatings on nanomaterials for biomedical applications has also been discussed, and the latest research results have been reported. Full article
(This article belongs to the Special Issue Polymer-Based Biocompatible System)
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<p>(<b>a</b>) electrospinning process, (<b>b</b>) photograph of the large-scale prepared mat of highly aligned PVDF NFs arrays; enlarged view exhibits the structure from respective section, (<b>c</b>) structure of oxidant-contained yellowish PVDF NFs mat before PANI coating, (<b>d</b>) VPP process, (<b>e</b>) structure of deepbluish PVDF NFs mat after PANI coating, (<b>f</b>) electrode assembling, (<b>g</b>) lamination process, (<b>h</b>) PDMS encapsulation of POESS design, (<b>i</b>) photographs of POESS with demonstration of flexibility. Schematic illustration of the piezo-organic-e-skin sensor design architecture. (Reprinted with permission from [<a href="#B45-polymers-12-03061" class="html-bibr">45</a>] Copyright (2020), American Chemical Society.).</p> Full article ">Figure 2
<p>Viability of (<b>a</b>) HeLa cells and (<b>b</b>) MC3T3 cells on PVDF and PVDF:CP electrospun fibers (control: PVDF). ** and **** signifies <span class="html-italic">p</span> &lt; 0.01 (1d) and <span class="html-italic">p</span> &lt; 0.0001 (1d), respectively, for both HeLa and MC3T3 culture (1d); #### signifies <span class="html-italic">p</span> &lt; 0.0001 (3d). CP, conducting polymers; PVDF, poly(vinylidene fluoride) (Reprinted with permission from [<a href="#B47-polymers-12-03061" class="html-bibr">47</a>] Copyright (2020), John Wiley and Sons.)</p> Full article ">Figure 3
<p>Multiscale mechanical analysis of polymethyl methacrylate layers grafted on Ti substrates. (Reprinted with permission from [<a href="#B14-polymers-12-03061" class="html-bibr">14</a>] Copyright (2017), Elsevier).</p> Full article ">Figure 4
<p>(<b>a</b>) Schematic illustration of polymethyl methacrylate/chitosan-silver (PMMA/AgNPs-CS) coating and its antibacterial activity; (<b>b</b>) optical density of suspension of <span class="html-italic">Escherichia coli</span> and <span class="html-italic">Staphylococcus aureus</span>. (Reprinted with permission from [<a href="#B56-polymers-12-03061" class="html-bibr">56</a>] Copyright (2019), Elsevier).</p> Full article ">Figure 5
<p>Scanning electron microscopy (<b>A</b>,<b>B</b>) and atomic force microscopy (<b>C</b>,<b>D</b>) images of poly(styryl bisphosphonate) (poly(StBP))-6, and poly(StBP)-40 (<b>D</b>) films, respectively, where “6” and “40” represent the thickness of the Mayer rod (6 and 40 µm) used to spread the polymer solution. (Reprinted with permission from [<a href="#B62-polymers-12-03061" class="html-bibr">62</a>] Copyright (2020), Elsevier).</p> Full article ">Figure 6
<p>Schematic illustration of polydimethylsiloxane (PDMS) coating using engineered anchor peptides fused to the cell-adhesive peptide sequence (glycine-arginine-glycine-aspartateserine, GRGDS). (Reprinted with permission from [<a href="#B63-polymers-12-03061" class="html-bibr">63</a>] Copyright (2019), American Chemical Society).</p> Full article ">Figure 7
<p>Schematic illustration of polydimethylsiloxane (PDMS) surface modification using hyaluronic acid and polydopamine (HA/PDA) composite coatings. (Reprinted with permission from [<a href="#B67-polymers-12-03061" class="html-bibr">67</a>]. Copyright (2017), American Chemical Society).</p> Full article ">Figure 8
<p>Schematic illustration of the cell trapping mechanism in polydimethylsiloxane (PDMS) microwells and the corresponding micrographs in (<b>a</b>) 200 µm and (<b>b</b>) 35 µm square microwell arrays. (<b>c</b>) Single-cell trapping demonstrated using a combination of bright field microscopy and fluorescence imaging. (Reprinted with permission from [<a href="#B68-polymers-12-03061" class="html-bibr">68</a>] Copyright (2018), American Institute of Physics).</p> Full article ">Figure 9
<p>Different approaches of chitosan coatings for nanoparticles. (Reprinted with permission from [<a href="#B90-polymers-12-03061" class="html-bibr">90</a>] Copyright (2020), Elsevier).</p> Full article ">Figure 10
<p>Schematic illustration of iron oxide nanorods coated with linear bisphosphonate−poly(ethylene glycol) (OPT), polyacrylic sodium salt (PAA), and polymethacrylate backbone/PEG side chain comb polymer (PCP). (Reprinted with permission from [<a href="#B97-polymers-12-03061" class="html-bibr">97</a>]. Copyright (2018), American Chemical Society).</p> Full article ">Figure 11
<p>Schematic illustration of imatinib mesylate (IM)-loaded PSS/PEI-AuNPs delivering IM to the layers of skin in melanoma treatment. (Reprinted with permission from [<a href="#B102-polymers-12-03061" class="html-bibr">102</a>]. Copyright (2015), American Chemical Society).</p> Full article ">
15 pages, 4698 KiB  
Article
A Preliminary Study of the Influence of Graphene Nanoplatelet Specific Surface Area on the Interlaminar Fracture Properties of Carbon Fiber/Epoxy Composites
by Konstantina Zafeiropoulou, Christina Kostagiannakopoulou, George Sotiriadis and Vassilis Kostopoulos
Polymers 2020, 12(12), 3060; https://doi.org/10.3390/polym12123060 - 21 Dec 2020
Cited by 10 | Viewed by 2659
Abstract
Graphene nanoplatelets (GNPs) are of particular interest to the field of nano-reinforced composites since they possess superior mechanical, fracture, thermal, and barrier properties. Due to their geometrical characteristics, high aspect ratio (AR)/specific surface area (SSA) and their planar structure, GNPs are considered as [...] Read more.
Graphene nanoplatelets (GNPs) are of particular interest to the field of nano-reinforced composites since they possess superior mechanical, fracture, thermal, and barrier properties. Due to their geometrical characteristics, high aspect ratio (AR)/specific surface area (SSA) and their planar structure, GNPs are considered as high-potential nanosized fillers for improving performance of composites. The present study investigates the effect of SSA of GNPs on fracture properties of carbon fiber reinforced polymers (CFRPs). For this reason, two nano-doped CFRPs were produced by using two types of GNPs (C300 and C500) with different SSAs, 300 and 500 m2/g, respectively. Both types of GNPs, at the same content of 0.5 wt%, were added into the epoxy matrix of composites by applying a three-roll milling technique. The nanomodified matrix was used for the manufacturing of prepregs, while the final composite laminates were fabricated through the vacuum-bag method. Mode I and II interlaminar fracture tests were carried out to determine the interlaminar fracture toughness GIC and GIIC of the composites, respectively. According to the results, the toughening effect of C500 GNPs was the strongest, resulting in increases of 25% in GIC and 33% in GIIC compared with the corresponding unmodified composites. The activation of the absorption mechanisms of C500 contributed to this outcome, which was confirmed by the scanning electron microscopy (SEM) analyses conducted in the fracture surfaces of specimens. On the other hand, C300 GNPs, due to disability to be dispersed uniformly into the epoxy matrix, did not influence the fracture properties of CFRPs, indicating that probably there is a threshold in SSA which is necessary to achieve for improving the fracture properties of CFRPs. Full article
(This article belongs to the Collection Reinforced Polymer Composites)
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<p>Schematic presentation of fabrication of prepregs with an in-house technique.</p> Full article ">Figure 2
<p>C-scan representation of the manufactured composites, (<b>a</b>) neat, (<b>b</b>) C300, and (<b>c</b>) C500, and the illustration of the manufactured composites, (<b>d</b>) neat, (<b>e</b>) C300, and (<b>f</b>) C500.</p> Full article ">Figure 3
<p>Specimen geometry for fracture toughness Mode I test.</p> Full article ">Figure 4
<p>Specimen geometry for fracture toughness Mode II test.</p> Full article ">Figure 5
<p>Load-displacement curves of representative specimens under DCB tests.</p> Full article ">Figure 6
<p>Load-displacement curves of representative specimens under ENF tests.</p> Full article ">Figure 7
<p>SEM images of representative fracture surfaces of, (<b>a</b>,<b>b</b>) neat composite, (<b>c</b>,<b>d</b>) 0.5 wt% C300 nano-modified composite, and (<b>e</b>,<b>f</b>) 0.5 wt% C500 nano-modified composite.</p> Full article ">Figure 8
<p>SEM images of C300 nano-fillers failure mechanisms: (<b>a</b>) crack pinning and bifurcation and (<b>b</b>) separation of graphene sheets and pull-out.</p> Full article ">Figure 9
<p>SEM images of C500 nano-fillers failure mechanisms: (<b>a</b>,<b>b</b>) crack pinning and bifurcation and (<b>c</b>,<b>d</b>) separation of graphene sheets and pull-out.</p> Full article ">Figure 10
<p>SEM image of C300 nano-fillers agglomerate 9.5 μm in size.</p> Full article ">
13 pages, 2085 KiB  
Article
Effects of Bromination-Dehydrobromination on the Microstructure of Isotropic Pitch Precursors for Carbon Fibers
by Dingcheng Liang, Deqian Liu, Shuai Yang, Changyu Lu, Qiang Xie and Jinchang Liu
Polymers 2020, 12(12), 3059; https://doi.org/10.3390/polym12123059 - 20 Dec 2020
Cited by 14 | Viewed by 2729
Abstract
In this work, isotropic pitch precursors are synthesized by the bromination-debromination method with ethylene bottom oil (EO) as the raw material and bromine as the initiator for pitch formation and condensation reactions. The aggregation structure, molecular weight distribution, and molecular structure of isotropic [...] Read more.
In this work, isotropic pitch precursors are synthesized by the bromination-debromination method with ethylene bottom oil (EO) as the raw material and bromine as the initiator for pitch formation and condensation reactions. The aggregation structure, molecular weight distribution, and molecular structure of isotropic pitch precursors are characterized by thermal mechanical analyzer (TMA), MALDI TOF-MS, and 13C NMR, respectively, for revealing the mechanism of synthesis of isotropic pitch precursors. The results show that at low bromine concentrations, polycyclic aromatic hydrocarbons (PAHs) were mainly ordered in cross-linked structures by bromination-debromination through substitution reactions of side chains. The condensed reactivity can be improved by the effect of bromine, meaning that condensation reaction was aggravated by the method of bromination-dehydrobromination. In the presence of excess bromine, the cross-linked stereo structure of PAHs changed to the planar structure of condensed PAHs, which was not conducive to the subsequent spinning and preparation of carbon fibers. Full article
(This article belongs to the Section Polymer Physics and Theory)
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<p>The preparation process of isotropic pitch precursors by bromination-dehydrobromination.</p> Full article ">Figure 2
<p>Schematic diagram of thermal mechanical analyzer (TMA) for isotropic pitch precursor characterization.</p> Full article ">Figure 3
<p>Thermal properties of isotropic pitch precursors characterized by thermomechanical analysis, (<b>a</b>) TMA curve and (<b>b</b>) DTMA curve.</p> Full article ">Figure 4
<p>Effects of bromination-dehydrobromination on the microstructure of isotropic pitch precursors.</p> Full article ">Figure 5
<p>The molecular weight distribution of isotropic pitch precursors by MALDI TOF-MS.</p> Full article ">Figure 6
<p><sup>13</sup>C NMR spectra of isotropic pitch precursors.</p> Full article ">
14 pages, 2651 KiB  
Article
The Investigation of the Silica-Reinforced Rubber Polymers with the Methoxy Type Silane Coupling Agents
by Sang Yoon Lee, Jung Soo Kim, Seung Ho Lim, Seong Hyun Jang, Dong Hyun Kim, No-Hyung Park, Jae Woong Jung and Jun Choi
Polymers 2020, 12(12), 3058; https://doi.org/10.3390/polym12123058 - 20 Dec 2020
Cited by 35 | Viewed by 5392
Abstract
The methoxy-type silane coupling agents were synthesized via the modification of the hydrolyzable group and characterized to investigate the change in properties of silica/rubber composites based on the different silane coupling agent structures and the masterbatch fabrication methods. The prepared methoxy-type silane coupling [...] Read more.
The methoxy-type silane coupling agents were synthesized via the modification of the hydrolyzable group and characterized to investigate the change in properties of silica/rubber composites based on the different silane coupling agent structures and the masterbatch fabrication methods. The prepared methoxy-type silane coupling agents exhibited higher reactivity towards hydrolysis compared to the conventional ethoxy-type one which led to the superior silanization to the silica filler surface modified for the reinforcement of styrene-butadiene rubber. The silica/rubber composites based on these methoxy-type silane coupling agents had the characteristics of more developed vulcanization and mechanical properties when fabricated as masterbatch products for tread materials of automobile tire surfaces. In particular, the dimethoxy-type silane coupling agent showed more enhanced rubber composite properties than the trimethoxy-type one, and the environmentally friendly wet masterbatch fabrication process was successfully optimized. The reactivity of the synthesized silane coupling agents toward hydrolysis was investigated by FITR spectroscopic analysis, and the mechanical properties of the prepared silica-reinforced rubber polymers were characterized using a moving die rheometer and a universal testing machine. Full article
(This article belongs to the Special Issue Polymer-SiO₂ Composites)
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<p>The chemical structure of the conventional silane coupling agents (SCA)s.</p> Full article ">Figure 2
<p>The chemical structure of the prepared SCAs.</p> Full article ">Figure 3
<p>FTIR spectra for 1 h hydrolysis reactions of the SCAs: (<b>a</b>) TESPD; (<b>b</b>) TMSPD; (<b>c</b>) DMSPD; and (<b>d</b>) spontaneous reactions of samples 5 and 6 during 10 days.</p> Full article ">Figure 4
<p>Gel permeation chromatography (GPC) data for methoxy-type SCAs after condensation side reactions.</p> Full article ">Figure 5
<p>FTIR spectra of the modified silica cake with the prepared SCAs.</p> Full article ">Figure 6
<p>The evaluation of remaining silica content in the wet masterbatch (WMB) sample with methoxy-type SCAs.</p> Full article ">Figure 7
<p>(<b>a</b>) The moving die rheometer (MDR) data for dry masterbatch (DMB) and WMB with SCAs. (<b>b</b>) The stress–strain curve of samples T-1–T-5.</p> Full article ">Figure 8
<p>The comparison of the DMB and WMB fabrication processes.</p> Full article ">Figure 9
<p>Schematic of the bonding of SCAs to a silica surface and the side reaction of the modified silica.</p> Full article ">
15 pages, 3371 KiB  
Article
Personalised 3D Printed Fast-Dissolving Tablets for Managing Hypertensive Crisis: In-Vitro/In-Vivo Studies
by Amjad Hussain, Faisal Mahmood, Muhammad Sohail Arshad, Nasir Abbas, Nadia Qamar, Jahanzeb Mudassir, Samia Farhaj, Jorabar Singh Nirwan and Muhammad Usman Ghori
Polymers 2020, 12(12), 3057; https://doi.org/10.3390/polym12123057 - 20 Dec 2020
Cited by 19 | Viewed by 3724
Abstract
Hypertensive crisis (HC) is an emergency health condition which requires an effective management strategy. Over the years, various researchers have developed captopril based fast-dissolving formulations to manage HC; however, primarily, the question of personalisation remains unaddressed. Moreover, commercially these formulations are available as [...] Read more.
Hypertensive crisis (HC) is an emergency health condition which requires an effective management strategy. Over the years, various researchers have developed captopril based fast-dissolving formulations to manage HC; however, primarily, the question of personalisation remains unaddressed. Moreover, commercially these formulations are available as in fixed-dose combinations or strengths, so the titration of dose according to patient’s prerequisite is challenging to achieve. The recent emergence of 3D printing technologies has given pharmaceutical scientists a way forward to develop personalised medicines keeping in view patients individual needs. The current project, therefore, is aimed at addressing the limitations as mentioned above by developing fast-dissolving captopril tablets using 3D printing approach. Captopril unloaded (F1) and loaded (F2-F4) filaments were successfully produced with an acceptable drug loading and mechanical properties. Various captopril formulations (F2–F4) were successfully printed using fused deposition modelling technique. The results revealed that the formulations (F2 and F3) containing superdisintegrant had a faster extent of dissolution and in-vivo findings were endorsing these results. The present study has successfully exhibited the utilisation of additive manufacturing approach to mend the gap of personalisation and manufacturing fast-dissolving captopril 3D printed tablets. The procedure adopted in the present study may be used for the development of fused deposition modelling (FDM) based fast-dissolving 3D printed tablets. Full article
(This article belongs to the Special Issue Exploitation of Polymer Structure and Mechanics in Developing Medicines)
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<p>Differential scanning calorimetry (DSC) pattern of (a) captopril API (b) F2, (c) F3, and (d) F4.</p> Full article ">Figure 2
<p>X-ray powder diffraction (XRPD) pattern of (a) captopril API (b) F2, (c) F3, and (d) F4.</p> Full article ">Figure 3
<p>Scanning electron microscopy (SEM) pictures of extruded filaments: (<b>a</b>) F1, (<b>b</b>) F2, (<b>c</b>) F3, and (<b>d</b>) F4.</p> Full article ">Figure 4
<p>SEM micrographs of 3D printed captopril tablets with top and side view (<b>a</b>,<b>b</b>) F1, (<b>c</b>,<b>d</b>) F2, (<b>e</b>,<b>f</b>) F3, and (<b>g</b>,<b>h</b>) F4.</p> Full article ">Figure 5
<p>Surface texture images of 3D printed captopril tablets: (<b>a</b>) F1, (<b>b</b>) F2, (<b>c</b>) F3, and (<b>d</b>) F4.</p> Full article ">Figure 6
<p>Disintegration profiles of 3D printed captopril tablets (n = 3).</p> Full article ">Figure 7
<p>Dissolution profiles of captopril loaded filaments (n = 3).</p> Full article ">Figure 8
<p>Dissolution profiles of 3D printed captopril tablets (n = 3).</p> Full article ">Figure 9
<p>Drug absorption vs. time profiles of standard, F2, F3, and F4, 3D printed captopril tablets (n = 3).</p> Full article ">
16 pages, 5849 KiB  
Article
The Study of Physico-Mechanical Properties of Polylactide Composites with Different Level of Infill Produced by the FDM Method
by Anna Gaweł and Stanisław Kuciel
Polymers 2020, 12(12), 3056; https://doi.org/10.3390/polym12123056 - 20 Dec 2020
Cited by 15 | Viewed by 2627
Abstract
The aim of this study was to evaluate the changes in physical-mechanical properties of the samples manufactured by 3D printing technology with the addition of varying degrees of polylactide (PLA) infill (50, 70, 85 and 100%). Half of the samples were soaked in [...] Read more.
The aim of this study was to evaluate the changes in physical-mechanical properties of the samples manufactured by 3D printing technology with the addition of varying degrees of polylactide (PLA) infill (50, 70, 85 and 100%). Half of the samples were soaked in physiological saline. The material used for the study was neat PLA, which was examined in terms of hydrolytic degradation, crystallization, mechanical strength, variability of properties at elevated temperatures, and dissipation of mechanical energy depending on the performed treatment. A significant impact of the amount of infill on changeable mechanical properties, such as hydrolytic degradation and crystallization was observed. The FDM printing method allows for waste–free production of light weight unit products with constant specyfic strength. Full article
(This article belongs to the Special Issue 3D and 4D Printing of (Bio)Materials II)
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<p>Comparison of the impact of the percent of added infill on Vicat Temperature.</p> Full article ">Figure 2
<p>Comparison of mechanical properties examined during static tensile test for untreated and crystallized samples measured at 70 °C.</p> Full article ">Figure 3
<p>DSC thermal curves for pure PLA (green curve) and PLA after crystallization process (red curve).</p> Full article ">Figure 4
<p>Weight gain resulting from hydrolytic degradation after soaking pure and crystallized samples for 1 and 28 d.</p> Full article ">Figure 5
<p>Comparison of mechanical properties examined during static tensile tests conducted at room temperature for pure, hydrolytically degraded and crystallized samples.</p> Full article ">Figure 6
<p>Comparison of mechanical properties examined during static tensile tests conducted at room temperature for pure, hydrolytically biodegraded and crystallized samples.</p> Full article ">Figure 7
<p>Impact strength depending on the percent of added infill and crystallinity of samples.</p> Full article ">Figure 8
<p>Influence of the percent of infill added to the samples produced by 3D printing on the shape of the hysteresis loops obtained after 1<sup>st</sup> and 50<sup>th</sup> load cycles Solid line—first loop, dashed line—fiftieth line.</p> Full article ">Figure 9
<p>Stretch fracture images showing the changes triggered by the successive increase in the percent of added infill on SEM images at 35 × magnification.</p> Full article ">Figure 10
<p>Stretch fracture images for the successive increase in the percent of added infill on SEM images at 100 × magnification.</p> Full article ">Figure 11
<p>Exemplary SEM image showing how to calculate the real amount of infill in the image using the ImageJ program.</p> Full article ">Figure 12
<p>Comparison of the real and assumed amount of infill and Feret coefficient.</p> Full article ">
23 pages, 4723 KiB  
Review
Advancements in the Blood–Brain Barrier Penetrating Nanoplatforms for Brain Related Disease Diagnostics and Therapeutic Applications
by Suresh Thangudu, Fong-Yu Cheng and Chia-Hao Su
Polymers 2020, 12(12), 3055; https://doi.org/10.3390/polym12123055 - 20 Dec 2020
Cited by 45 | Viewed by 8345
Abstract
Noninvasive treatments to treat the brain-related disorders have been paying more significant attention and it is an emerging topic. However, overcoming the blood brain barrier (BBB) is a key obstacle to most of the therapeutic drugs to enter into the brain tissue, which [...] Read more.
Noninvasive treatments to treat the brain-related disorders have been paying more significant attention and it is an emerging topic. However, overcoming the blood brain barrier (BBB) is a key obstacle to most of the therapeutic drugs to enter into the brain tissue, which significantly results in lower accumulation of therapeutic drugs in the brain. Thus, administering the large quantity/doses of drugs raises more concerns of adverse side effects. Nanoparticle (NP)-mediated drug delivery systems are seen as potential means of enhancing drug transport across the BBB and to targeted brain tissue. These systems offer more accumulation of therapeutic drugs at the tumor site and prolong circulation time in the blood. In this review, we summarize the current knowledge and advancements on various nanoplatforms (NF) and discusses the use of nanoparticles for successful cross of BBB to treat the brain-related disorders such as brain tumors, Alzheimer’s disease, Parkinson’s disease, and stroke. Full article
(This article belongs to the Special Issue Intelligent Polymeric Delivery System for Biomedical Applications)
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<p>Structure of the blood brain barrier (BBB) and transport pathways across the BBB. Reproduced with permission from Reference [<a href="#B14-polymers-12-03055" class="html-bibr">14</a>].</p> Full article ">Figure 2
<p>Schematic illustration of the blood brain barrier (BBB)-penetrating nanoplatforms (NFs) for targeted delivery and therapeutics into the brain tissue to treat brain-related disorders.</p> Full article ">Figure 3
<p>In vivo anti-tumor activity of G23-Dox/alg-Fe<sub>3</sub>O<sub>4</sub> NPs. (<b>A</b>) Schematic representation of synthesis process and BBB penetrating Dox delivery. (<b>B</b>) In vivo MRI contrast imaging abilities of alg-Fe<sub>3</sub>O<sub>4</sub> NPs and G23-alg-Fe<sub>3</sub>O<sub>4</sub> NPs. (<b>C</b>) In vivo luminescence images show from U87MG-luc2 cells monitored using the IVIS imaging system after mice were intravenously injected with G23-Dox/alg-Fe<sub>3</sub>O<sub>4</sub> NPs for seven days. (<b>D</b>) Body weights of mice during the treatment. Reproduced with permission from Reference [<a href="#B69-polymers-12-03055" class="html-bibr">69</a>].</p> Full article ">Figure 4
<p>Cell membranes coated on ICG loaded nanoparticle (PCL-ICG) nanoparticles (NPs). (<b>A</b>) Representative bioluminescence images of U87MG-Luc glioma-bearing mice in different groups: (1) phosphate buffered saline (PBS), (2) normal cell coated ICG loaded nanoparticle (COS7-PCL-ICG), (3) COS7-PCL-ICG + laser, (4) B16-PCL-ICG, and (5) B16-PCL-ICG + laser under 808-nm laser irradiation (1 W cm<sup>−2</sup>, 5 min). CICG = 1 mg kg<sup>−1</sup>. (<b>B</b>) Quantitative fluorescence signal intensity in the brain. Reproduced with permission from Reference [<a href="#B74-polymers-12-03055" class="html-bibr">74</a>].</p> Full article ">Figure 5
<p>Focused ultrasound-induced blood–brain barrier opening strategy. (<b>A</b>) Schematic representation of size-dependent nanoparticle (NP) delivery to the brain via a focused ultrasound (FUS). (<b>B</b>) TEM images of 3, 15, 120-nm sized Au NPs. (<b>C</b>) Distribution of Au NPs in mouse brains in vivo models. (<b>D</b>) Kinetic modeling studies of FUS-assisted NPs delivery into the brain. Reproduced with permission from Reference [<a href="#B104-polymers-12-03055" class="html-bibr">104</a>].</p> Full article ">Figure 6
<p>Zwitterionic poly(carboxybetaine) (PCB)-based nanoparticle (MCPZFS NPs) for treating Alzheimer’s disease (AD). (<b>A</b>) Schematic illustration of the MCPZFS NPs for AD. (<b>B</b>) Characterization of the NPs. (<b>C</b>) Effect of NPs on the inflammatory regulation of microglia and (<b>D</b>) the effect of NPs on phagocytosis and degradation of Aβ by microglia. Data are presented as the mean ± SD. * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.001. Reproduced with permission from Reference [<a href="#B117-polymers-12-03055" class="html-bibr">117</a>].</p> Full article ">Figure 7
<p>Dual-target traceable nanodrug for Parkinson’s disease (PD) treatment. (<b>A</b>) Schematic representation of synthesis of nanodrug and application for PD. (<b>B</b>) Systematic characterization of dual-target traceable nanodrug (B6ME-NPs). (<b>C</b>) Confocal microscopy (CSLM) and flow cytometry uptake studies to confirm the successful blood brain barrier (BBB) crossing. (<b>D</b>) Fluorescence and magnetic resonance (MR) images of the mice model after 24 h of i.v. injection of the nanodrug. Data are presented as the mean ± SD. * <span class="html-italic">p</span> &lt; 0.05, ** <span class="html-italic">p</span> &lt; 0.01, *** <span class="html-italic">p</span> &lt; 0.001. Reproduced with permission from Reference [<a href="#B124-polymers-12-03055" class="html-bibr">124</a>].</p> Full article ">Figure 8
<p>Schematic representation of magnetosome-like ferrimagnetic iron oxide nanochains (MFION)-based fabrication of Mesenchymal stem cells (MSCs) for the recovery of post-ischemic stroke. Reproduced with permission from Reference [<a href="#B151-polymers-12-03055" class="html-bibr">151</a>].</p> Full article ">
21 pages, 2735 KiB  
Article
Adenine as Epoxy Resin Hardener for Sustainable Composites Production with Recycled Carbon Fibers and Cellulosic Fibers
by Stefano Merighi, Laura Mazzocchetti, Tiziana Benelli and Loris Giorgini
Polymers 2020, 12(12), 3054; https://doi.org/10.3390/polym12123054 - 20 Dec 2020
Cited by 4 | Viewed by 3347
Abstract
In this work, Adenine is proposed, for the first time, as a cross-linker for epoxy resins. Adenine is an amino-substituted purine with heterocyclic aromatic structure showing both proton donors, and hydrogen bonding ability. DSC studies show that adenine is able to positively cross-link [...] Read more.
In this work, Adenine is proposed, for the first time, as a cross-linker for epoxy resins. Adenine is an amino-substituted purine with heterocyclic aromatic structure showing both proton donors, and hydrogen bonding ability. DSC studies show that adenine is able to positively cross-link a biobased DGEBA-like commercial epoxy precursor with good thermal performance and a reaction mechanism based on a 1H NMR investigation has been proposed. The use of such a formulation to produce composite with recycled short carbon fibers (and virgin ones for the sake of comparison), as well as jute and linen natural fibers as sustainable reinforcements, leads to materials with high compaction and fiber content. The curing cycle was optimized for both carbon fiber and natural fiber reinforced materials, with the aim to achieve the better final properties. All composites produced display good thermal and mechanical properties with glass transition in the range of HT resins (Tg > 150 °C, E’ =26 GPa) for the carbon fiber-based composites. The natural fiber-based composites display slightly lower performance that is nonetheless good compared with standard composite performance (Tg about 115–120 °C, E’ = 7–9 GPa). The present results thus pave the way to the application of adenine as hardener system for composites production. Full article
(This article belongs to the Special Issue Polymers from Renewable Sources and Their Mechanical Reinforcement)
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Figure 1
<p>DSC first (<b>A</b>) and second (<b>B</b>) DSC heating scans of CA1(<b><span style="color:red">—</span></b>), CA2 (<b><span style="color:blue">—</span></b>) and CA3 (<b><span style="color:#00B050">—</span></b>).</p> Full article ">Figure 2
<p><sup>1</sup>H NMR spectra of Adenine, GA4-0 (<b><span style="color:#4472C4">—</span></b>) and GA1-24 (<b><span style="color:#00B050">—</span></b>), GA4-24 (<b><span style="color:#92D050">—</span></b>), GA8-24 (<b><span style="color:#C00000">—</span></b>) after 24 h of reaction at 90 °C.</p> Full article ">Figure 3
<p>Magnification of <sup>1</sup>H NMR spectra (aromatic range) of GA4-0 (<b><span style="color:#0000CC">—</span></b>) and GA1-24 (<b><span style="color:#00B050">—</span></b>), GA4-24 (<b><span style="color:#99CC00">—</span></b>), GA8-24 (<b><span style="color:red">—</span></b>) after 24 h of reaction at 90°C.</p> Full article ">Figure 4
<p><sup>1</sup>H NMR spectra of GA4 at 0 (<b><span style="color:#7030A0">—</span></b>), 1 (<b><span style="color:blue">—</span></b>), 3 (<b><span style="color:#0070C0">—</span></b>), 5 (<b><span style="color:#00B050">—</span></b>), 7 (<b><span style="color:#99CC00">—</span></b>), and 9 (<b><span style="color:#C00000">—</span></b>) h of reaction at 90 °C.</p> Full article ">Figure 5
<p>TGA thermograms of CA-vCF (<b><span style="color:red">—</span></b>) and CA-rCF (—) composites. The dashed line represents the temperature program during the measurement, while the blue line shows the switch from nitrogen to air atmosphere. Curves displayed in the figure were selected to best fit the average values calculated for each batch of specimens.</p> Full article ">Figure 6
<p>TGA thermograms of CA-FF (<b><span style="color:green">—</span></b>) and CA-JF (<b><span style="color:blue">—</span></b>) composites. Curves displayed in the figure were selected to best fit the average values calculated for each batch of specimens.</p> Full article ">Figure 7
<p>DMA spectra of (<b>a</b>) carbon fibers (CA-vCF (<b>—</b>) and CA-rCF (<b><span style="color:red">—</span></b>)), and (<b>b</b>) natural fibers (CA-FF (<b><span style="color:blue">—</span></b>) and CA2-J (<b><span style="color:lime">—</span></b>))-based composites samples.</p> Full article ">Scheme 1
<p>Structure of Adenine (A).</p> Full article ">Scheme 2
<p>Possible reaction products between G2MPE and Adenine.</p> Full article ">Scheme 3
<p>General synthetic reaction mechanism of Adenine with epoxy derivatives.</p> Full article ">
17 pages, 8313 KiB  
Article
Crystallization and Thermal Behaviors of Poly(ethylene terephthalate)/Bisphenols Complexes through Melt Post-Polycondensation
by Shichang Chen, Shangdong Xie, Shanshan Guang, Jianna Bao, Xianming Zhang and Wenxing Chen
Polymers 2020, 12(12), 3053; https://doi.org/10.3390/polym12123053 - 19 Dec 2020
Cited by 17 | Viewed by 4415
Abstract
Three kinds of modified poly(ethylene terephthalate) (PET) were prepared by solution blending combined with melt post-polycondensation, using 4,4′-thiodiphenol (TDP), 4,4′-oxydiphenol (ODP) and hydroquinone (HQ) as the bisphenols, respectively. The effects of TDP, ODP and HQ on melt post-polycondensation process and crystallization kinetics, melting [...] Read more.
Three kinds of modified poly(ethylene terephthalate) (PET) were prepared by solution blending combined with melt post-polycondensation, using 4,4′-thiodiphenol (TDP), 4,4′-oxydiphenol (ODP) and hydroquinone (HQ) as the bisphenols, respectively. The effects of TDP, ODP and HQ on melt post-polycondensation process and crystallization kinetics, melting behaviors, crystallinity and thermal stability of PET/bisphenols complexes were investigated in detail. Excellent chain growth of PET could be achieved by addition of 1 wt% bisphenols, but intrinsic viscosity of modified PET decreased with further bisphenols content. Intermolecular hydrogen bonding between carbonyl groups of PET and hydroxyl groups of bisphenols were verified by Fourier transform infrared spectroscopy. Compare to pure PET, both the crystallization rate and melting temperatures of PET/bisphenols complexes were reduced obviously, suggesting an impeded crystallization and reduced lamellar thickness. Moreover, the structural difference between TDP, ODP and HQ played an important role on crystallization kinetics. It was proposed that the crystallization rate of TDP modified PET was reduced significantly due to the larger amount of rigid benzene ring and larger polarity than that of PET with ODP or HQ. X-ray diffraction results showed that the crystalline structure of PET did not change from the incorporation of bisphenols, but crystallinity of PET decreased with increasing bisphenols content. Thermal stability of modified PET declined slightly, which was hardly affected by the molecular structure of bisphenols. Full article
(This article belongs to the Special Issue Process–Structure–Properties in Polymer Additive Manufacturing)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>The intrinsic viscosity of PET modified by bisphenol compounds.</p> Full article ">Figure 2
<p>Differential scanning calorimeter (DSC) cooling curves obtained for PET and bisphenols/PET complexes at 10 °C/min: (<b>a</b>) TDP/PET, (<b>b</b>) ODP/PET and (<b>c</b>) HQ/PET.</p> Full article ">Figure 3
<p>Plot of (<b>a</b>) <span class="html-italic">T</span><sub>p</sub> and (<b>b</b>) <span class="html-italic">T</span><sub>onset</sub>−<span class="html-italic">T</span><sub>p</sub> as a function of content of bisphenols for PET and bisphenols/PET complexes.</p> Full article ">Figure 4
<p>DSC heating curves obtained for PET and bisphenols/PET complexes at 10 °C/min: (<b>a</b>) TDP/PET, (<b>b</b>) ODP/PET and (<b>c</b>) HQ/PET. (<b>d</b>) Plots of <span class="html-italic">T</span><sub>m</sub> as a function of the content of bisphenols.</p> Full article ">Figure 5
<p>DSC cooling curves at various cooling rates for TDP/PET complexes.</p> Full article ">Figure 6
<p>Plots of lg[−ln(1 − <span class="html-italic">X<sub>t</sub></span>)] against lgt for (<b>a</b>) PET, (<b>b</b>) TDP/PET, (<b>c</b>) ODP/PET and (<b>d</b>) HQ/PET at various cooling rates with a weight fraction of 4 wt%.</p> Full article ">Figure 7
<p>Plots of (<b>a</b>,<b>c</b>) <span class="html-italic">t</span><sub>1/2</sub> and (<b>b</b>,<b>d</b>) <span class="html-italic">Z</span><sub>c</sub> as a function of the cooling rate for PET and bisphenols/PET complexes.</p> Full article ">Figure 8
<p>Selected 2D wide-angle X-ray diffraction (WAXD) patterns of PET and bisphenols/PET complexes.</p> Full article ">Figure 9
<p>WAXD patterns for (<b>a</b>) TDP/PET, (<b>b</b>) ODP/PET, (<b>c</b>) HQ/PET and (<b>d</b>) typical fitting process with Pseudo-Voigt function.</p> Full article ">Figure 10
<p>Composition dependence of <span class="html-italic">X</span><sub>c</sub> of PET and bisphenols/PET complexes.</p> Full article ">Figure 11
<p>(<b>a</b>,<b>c</b>,<b>e</b>) Weight loss curves and (<b>b</b>,<b>d</b>,<b>f</b>) derivatives weight loss curves for PET and bisphenols/PET complexes.</p> Full article ">Scheme 1
<p>The chemical structure of bisphenols and PET.</p> Full article ">
18 pages, 8166 KiB  
Article
The Bonding Mechanism of the Micro-Interface of Polymer Coated Steel
by Jiyang Liu, Qingdong Zhang, Boyang Zhang and Mingyang Yu
Polymers 2020, 12(12), 3052; https://doi.org/10.3390/polym12123052 - 19 Dec 2020
Cited by 11 | Viewed by 8168
Abstract
As food and beverages require more and more green and safe packaging products, the emergence of polymer coated steel (PCS) has been promoted. PCS is a layered composite strip made of metal and polymer. To probe the bonding mechanism of PCS micro-interface, the [...] Read more.
As food and beverages require more and more green and safe packaging products, the emergence of polymer coated steel (PCS) has been promoted. PCS is a layered composite strip made of metal and polymer. To probe the bonding mechanism of PCS micro-interface, the substrate tin-free steel (TFS) was physically characterized by SEM and XPS, and cladding polyethylene terephthalate (PET) was simulated by first-principles methods of quantum mechanics (QM). We used COMPASS force field for molecular dynamics (MD) simulation. XPS pointed out that the element composition of TFS surface coating is Cr(OH)3, Cr2O3 and CrO3. The calculation results of MD and QM indicate that the chromium oxide and PET molecules compound in the form of acid-base interaction. The binding energies of Cr2O3 (110), (200), and (211) with PET molecules are −13.07 eV, −2.74 eV, and −2.37 eV, respectively. We established a Cr2O3 (200) model with different hydroxyl concentrations. It is proposed that the oxygen atom in C=O in the PET molecule combines with –OH on the surface of TFS to form a hydrogen bond. The binding energy of the PCS interface increases with the increase of the surface hydroxyl concentration of the TFS. It provides theoretical guidance and reference significance for the research on the bonding mechanism of PCS. Full article
(This article belongs to the Section Polymer Applications)
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<p>Equipment diagram and schematic diagram of the coating process.</p> Full article ">Figure 2
<p>Raw materials and polymer coated steel (PCS) samples.</p> Full article ">Figure 3
<p>Schematic diagram of the tin free steel (TFS) surface coating structure.</p> Full article ">Figure 4
<p>Polyethylene terephthalate (PET) molecular formula and model diagram (white is H atom, red is O atom, gray is C atom).</p> Full article ">Figure 5
<p>Cr<sub>2</sub>O<sub>3</sub> surface model diagram (red is O atom, gray is Cr atom).</p> Full article ">Figure 6
<p>The SEM images of blank steel and TFS.</p> Full article ">Figure 7
<p>The SEM images and EDS curve of the blank steel and TFS.</p> Full article ">Figure 8
<p>XPS spectra of the TFS surface.</p> Full article ">Figure 9
<p>The XPS spectra of Cr in the TFS.</p> Full article ">Figure 10
<p>The fitting curve of the Cr XPS in the TFS.</p> Full article ">Figure 11
<p>The initial and final configurations of the Cr<sub>2</sub>O<sub>3</sub> (110) (<b>a</b>,<b>a′</b>,<b>a″</b>) surface, Cr<sub>2</sub>O<sub>3</sub> (200) (<b>b</b>,<b>b′</b>,<b>b″</b>) surface and Cr<sub>2</sub>O<sub>3</sub> (211) (<b>c</b>,<b>c′</b>,<b>c″</b>) surface interacting with PET molecules (white is H atom, red is O atom, gray is C atom).</p> Full article ">Figure 12
<p>The binding energy of the Cr<sub>2</sub>O<sub>3</sub> surface with PET.</p> Full article ">Figure 13
<p>Concentration profiles of oxygen (O) and hydrogen (H) atoms in PET on top of (<b>a</b>) Cr<sub>2</sub>O<sub>3</sub> (110), (<b>b</b>) Cr<sub>2</sub>O<sub>3</sub> (200), and (<b>c</b>) Cr<sub>2</sub>O<sub>3</sub> (211) surfaces before (O and H) and after (Of and Hf) MD simulations.</p> Full article ">Figure 14
<p>GGA/PW91-optimized structure and highest occupied molecular orbitals (HOMOs) and lowest occupied molecular orbital (LUMOs) of PET molecules.</p> Full article ">Figure 15
<p>Partial atomic charge of PET molecules.</p> Full article ">Figure 16
<p>Cr<sub>2</sub>O<sub>3</sub> (200) surface with different hydroxyl concentration (white is H atom, red is O atom, gray is C atom).</p> Full article ">Figure 17
<p>Side view of PET molecule complexation with Cr<sub>2</sub>O<sub>3</sub> with different hydroxyl concentration (the cyan dotted line represents the hydrogen bond).</p> Full article ">Figure 18
<p>Different concentrations of hydroxyl groups.</p> Full article ">
10 pages, 1924 KiB  
Review
Modified Fish Gelatin as an Alternative to Mammalian Gelatin in Modern Food Technologies
by Svetlana R. Derkach, Nikolay G. Voron’ko, Yuliya A. Kuchina and Daria S. Kolotova
Polymers 2020, 12(12), 3051; https://doi.org/10.3390/polym12123051 - 19 Dec 2020
Cited by 81 | Viewed by 6605
Abstract
This review considers the main properties of fish gelatin that determine its use in food technologies. A comparative analysis of the amino acid composition of gelatin from cold-water and warm-water fish species, in comparison with gelatin from mammals, which is traditionally used in [...] Read more.
This review considers the main properties of fish gelatin that determine its use in food technologies. A comparative analysis of the amino acid composition of gelatin from cold-water and warm-water fish species, in comparison with gelatin from mammals, which is traditionally used in the food industry, is presented. Fish gelatin is characterized by a reduced content of proline and hydroxyproline which are responsible for the formation of collagen-like triple helices. For this reason, fish gelatin gels are less durable and have lower gelation and melting temperatures than mammalian gelatin. These properties impose significant restrictions on the use of fish gelatin in the technology of gelled food as an alternative to porcine and bovine gelatin. This problem can be solved by modifying the functional characteristics of fish gelatin by adding natural ionic polysaccharides, which, under certain conditions, are capable of forming polyelectrolyte complexes with gelatin, creating additional nodes in the spatial network of the gel. Full article
(This article belongs to the Special Issue Biopolymers for Medicinal, Macromolecules, and Food Applications)
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<p>Dependencies of storage G′ (1) and loss G″ (2) moduli on the concentration of sodium alginate C<sub>SA</sub> in fish gelatin gels at 4 °C (<b>a</b>) and 14 °C (<b>b</b>). Gelatin concentration is 10 wt%.</p> Full article ">Figure 2
<p>Schematic model of the formation of a complex κ-carrageenan–gelatin gel network.</p> Full article ">
21 pages, 2919 KiB  
Article
The Effect of Halloysite Nanotubes on the Fire Retardancy Properties of Partially Biobased Polyamide 610
by David Marset, Celia Dolza, Eduardo Fages, Eloi Gonga, Oscar Gutiérrez, Jaume Gomez-Caturla, Juan Ivorra-Martinez, Lourdes Sanchez-Nacher and Luis Quiles-Carrillo
Polymers 2020, 12(12), 3050; https://doi.org/10.3390/polym12123050 - 19 Dec 2020
Cited by 16 | Viewed by 3018
Abstract
The main objective of the work reported here was the analysis and evaluation of halloysite nanotubes (HNTs) as natural flame retardancy filler in partially biobased polyamide 610 (PA610), with 63% of carbon from natural sources. HNTs are naturally occurring clays with a nanotube-like [...] Read more.
The main objective of the work reported here was the analysis and evaluation of halloysite nanotubes (HNTs) as natural flame retardancy filler in partially biobased polyamide 610 (PA610), with 63% of carbon from natural sources. HNTs are naturally occurring clays with a nanotube-like shape. PA610 compounds containing 10%, 20%, and 30% HNT were obtained in a twin-screw co-rotating extruder. The resulting blends were injection molded to create standard samples for fire testing. The incorporation of the HNTs in the PA610 matrix leads to a reduction both in the optical density and a significant reduction in the number of toxic gases emitted during combustion. This improvement in fire properties is relevant in applications where fire safety is required. With regard to calorimetric cone results, the incorporation of 30% HNTs achieved a significant reduction in terms of the peak values obtained of the heat released rate (HRR), changing from 743 kW/m2 to about 580 kW/m2 and directly modifying the shape of the characteristic curve. This improvement in the heat released has produced a delay in the mass transfer of the volatile decomposition products, which are entrapped inside the HNTs’ lumen, making it difficult for the sample to burn. However, in relation to the ignition time of the samples (TTI), the incorporation of HNTs reduces the ignition start time about 20 s. The results indicate that it is possible to obtain polymer formulations with a high renewable content such as PA610, and a natural occurring inorganic filler in the form of a nanotube, i.e., HNTs, with good flame retardancy properties in terms of toxicity, optical density and UL94 test. Full article
(This article belongs to the Special Issue Biopolymers from Natural Resources)
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<p>Heat release rate as a function of time.</p> Full article ">Figure 2
<p>Effective heat of combustion as a function of time.</p> Full article ">Figure 3
<p>CO<sub>2</sub> production during the CCT test: (<b>a</b>) CO<sub>2</sub> rate and (<b>b</b>) CO<sub>2</sub> yield.</p> Full article ">Figure 4
<p>CO production during the CCT test: (<b>a</b>) CO rate and (<b>b</b>) CO yield.</p> Full article ">Figure 5
<p>Smoke production rate of samples with HNTs.</p> Full article ">Figure 6
<p>Specific extinction area for PA610 samples loaded with HNTs.</p> Full article ">Figure 7
<p>(<b>a</b>) Percentage of residual mass during the testing of PA610 samples with HNTs; (<b>b</b>) Loss of mass ratio of PA610 samples with HNTs.</p> Full article ">Figure 8
<p>Visual difference between samples before and after the CCT test: (<b>a</b>) PA1010 before, (<b>b</b>) PA1010 /10HNTs before, (<b>c</b>) PA1010/20HNTs before, (<b>d</b>) PA1010/30HNTs before and (<b>e</b>) PA1010 after, (<b>f</b>) PA1010/10HNTs after, (<b>g</b>) PA1010/20HNTs after, (<b>h</b>) PA1010/30HNTs after.</p> Full article ">Figure 9
<p>Graphic representation of the limiting oxygen index (LOI) values of each sample.</p> Full article ">Figure 10
<p>Evolution of optical density as a function of time.</p> Full article ">Figure 11
<p>Scheme of the fire retardancy enhancement by HNTs by the entrapment of volatile decomposition products and delaying the mass transfer in (<b>a</b>) bioPA610 and (<b>b</b>) bioPA610+HNTs.</p> Full article ">
22 pages, 4508 KiB  
Article
A Highly Efficient Ag Nanoparticle-Immobilized Alginate-g-Polyacrylonitrile Hybrid Photocatalyst for the Degradation of Nitrophenols
by Imran Hasan, Charu Shekhar, Walaa Alharbi, Maymonah Abu Khanjer, Rais Ahmad Khan and Ali Alsalme
Polymers 2020, 12(12), 3049; https://doi.org/10.3390/polym12123049 - 19 Dec 2020
Cited by 16 | Viewed by 2303
Abstract
Herein, we report PAN-g-Alg@Ag-based nanocatalysts synthesis via in situ oxidative free-radical polymerization of acrylonitrile (AN) using Alg@Ag nanoparticles (Alg@Ag NPs). Various analytical techniques, including FTIR, XRD, SEM, TEM, UV–Vis, and DSC, were employed to determine bonding interactions and chemical characteristics of the nanocatalyst. [...] Read more.
Herein, we report PAN-g-Alg@Ag-based nanocatalysts synthesis via in situ oxidative free-radical polymerization of acrylonitrile (AN) using Alg@Ag nanoparticles (Alg@Ag NPs). Various analytical techniques, including FTIR, XRD, SEM, TEM, UV–Vis, and DSC, were employed to determine bonding interactions and chemical characteristics of the nanocatalyst. The optimized response surface methodology coupled central composite design (RSM–CCD) reaction conditions were a 35-min irradiation time in a 70-mg L−1 2,4-dinitrophenol (DNP) solution at pH of 4.68. Here, DNP degradation was 99.46% at a desirability of 1.00. The pseudo-first-order rate constant (K1) values were 0.047, 0.050, 0.054, 0.056, 0.059, and 0.064 min−1 with associated half-life (t1/2) values of 14.74, 13.86, 12.84, 12.38, 11.74, 10.82, and 10.04 min that corresponded to DNP concentrations of 10, 20, 30, 40, 50, 60, and 70 mg L−1, respectively, in the presence of PAN-g-Alg@Ag (0.03 g). The results indicate that the reaction followed the pseudo-first-order kinetic model with an R2 value of 0.99. The combined absorption properties of PAN and Alg@Ag NPs on copolymerization on the surface contributed more charge density to surface plasmon resonance (SPR) in a way to degrade more and more molecules of DNP together with preventing the recombination of electron and hole pairs within the photocatalytic process. Full article
(This article belongs to the Section Polymer Chemistry)
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<p>FTIR spectra of: (<b>a</b>) sodium alginate; (<b>b</b>) Alg@Ag NPs; (<b>c</b>) poly(acrylonitrile); and (<b>d</b>) PAN-g-Alg@Ag.</p> Full article ">Figure 2
<p>XRD spectra of: (<b>a</b>) Alg@Ag NPs; (<b>b</b>) poly(acrylonitrile); and (<b>c</b>) PAN-g-Alg@Ag.</p> Full article ">Figure 3
<p>SEM images of: (<b>a</b>) sodium alginate; (<b>b</b>) poly(acrylonitrile); and (<b>c</b>) PAN-g-Alg@Ag. (<b>d</b>) The EDX spectrum of PAN-g-Alg@Ag.</p> Full article ">Figure 4
<p>TEM images of the PAN-g-Alg@Ag nanocomposite.</p> Full article ">Figure 5
<p>UV–Vis spectrum of alginate (black line), PAN (Red line), Alg@Ag NPs (blue line), and PAN-g-Alg@Ag NC (green line).</p> Full article ">Figure 6
<p>DSC spectrum of the PAN-g-Alg@Ag NCs.</p> Full article ">Figure 7
<p>(<b>a</b>,<b>b</b>) 3D surface interactive plot of the irradiation time vs. solution pH and a plot of the solution pH vs. the DNP concentration; (<b>c</b>) interaction curves of all three reaction variables, namely irradiation time, solution pH, and DNP concentration; and (<b>d</b>) normal probability plot depicting the data points along the straight line.</p> Full article ">Figure 7 Cont.
<p>(<b>a</b>,<b>b</b>) 3D surface interactive plot of the irradiation time vs. solution pH and a plot of the solution pH vs. the DNP concentration; (<b>c</b>) interaction curves of all three reaction variables, namely irradiation time, solution pH, and DNP concentration; and (<b>d</b>) normal probability plot depicting the data points along the straight line.</p> Full article ">Figure 8
<p>(<b>a</b>) UV–Vis action curve for irradiation time; (<b>b</b>) UV–Vis action curve for variable concentration of DNP; (<b>c</b>) Ce/Co vs. irradiation curve; and (<b>d</b>) pseudo-first order kinetic ci = curve for variable concentration of DNP.</p> Full article ">Figure 9
<p>(<b>a</b>) UV–Vis plot for the photocatalytic activity of synthesized PAN-g-Alg@Ag NC and its individual constituents towards DNP; and (<b>b</b>) the corresponding percent degradation bar graph.</p> Full article ">Figure 10
<p>(<b>a</b>) UV–Vis plot; and (<b>b</b>) degradation rate of DNP in direct solar irradiation without catalyst (photolysis, A), dark with catalyst (B), and direct solar irradiation with catalyst (C) for an aliquot of 20 mL of 70 mg L<sup>−1</sup> DNP under optimized reaction conditions.</p> Full article ">Figure 11
<p>Photodegradation mechanism of DNP by PAN-g-Alg@Ag under direct solar irradiation.</p> Full article ">
16 pages, 4963 KiB  
Article
Structural Optimization through Biomimetic-Inspired Material-Specific Application of Plant-Based Natural Fiber-Reinforced Polymer Composites (NFRP) for Future Sustainable Lightweight Architecture
by Timo Sippach, Hanaa Dahy, Kai Uhlig, Benjamin Grisin, Stefan Carosella and Peter Middendorf
Polymers 2020, 12(12), 3048; https://doi.org/10.3390/polym12123048 - 19 Dec 2020
Cited by 24 | Viewed by 5101
Abstract
Under normal conditions, the cross-sections of reinforced concrete in classic skeleton construction systems are often only partially loaded. This contributes to non-sustainable construction solutions due to an excess of material use. Novel cross-disciplinary workflows linking architects, engineers, material scientists and manufacturers could offer [...] Read more.
Under normal conditions, the cross-sections of reinforced concrete in classic skeleton construction systems are often only partially loaded. This contributes to non-sustainable construction solutions due to an excess of material use. Novel cross-disciplinary workflows linking architects, engineers, material scientists and manufacturers could offer alternative means for more sustainable architectural applications with extra lightweight solutions. Through material-specific use of plant-based Natural Fiber-Reinforced Polymer Composites (NFRP), also named Biocomposites, a high-performance lightweight structure with topology optimized cross-sections has been here developed. The closed life cycle of NFRPs promotes sustainability in construction through energy recovery of the quickly generative biomass-based materials. The cooperative design resulted in a development that were verified through a 1:10 demonstrator, whose fibrous morphology was defined by biomimetically-inspired orthotropic tectonics, generated with by the fiber path optimization software tools, namely EdoStructure and EdoPath in combination with the appliance of the digital additive manufacturing technique: Tailored Fiber Placement (TFP). Full article
(This article belongs to the Special Issue Functional Polymer Composites)
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<p>Unsustainable construction ethics.</p> Full article ">Figure 2
<p>Applications of Tailored Fiber Placement (TFP): (<b>a</b>) Tailored Biocomposite Mock-up 2019, BioMat, at ITKE, University of Stuttgart; Single-curved lightweight structure, of 225 cm high and 125 cm width [<a href="#B7-polymers-12-03048" class="html-bibr">7</a>]. (<b>b</b>) Bango sound distribution element, Institute of Aircraft Design (IFB), University of Stuttgart; Material and geometry distribute sound waves over various surfaces [<a href="#B17-polymers-12-03048" class="html-bibr">17</a>]. (<b>c</b>) Flax fibers are shown, being the first leading industrial natural fiber in the automotive industry applied in two thirds of the overall natural fiber-reinforced polymer (NFRP) applied in this industry [<a href="#B18-polymers-12-03048" class="html-bibr">18</a>].</p> Full article ">Figure 3
<p>Demonstration of the applied interdisciplinary workflow.</p> Full article ">Figure 4
<p>Biological and computational structural optimization. (<b>a</b>) Phytoplankton Emiliania Huxley, 10 µm, marine calcite organism composed of a series of coccoliths [<a href="#B35-polymers-12-03048" class="html-bibr">35</a>]; (<b>b</b>) Topologic optimized design proposal.</p> Full article ">Figure 5
<p>Topology optimization workflow: (<b>a</b>) initial domain design; (<b>b</b>) parametric form-finding with FEM on restricted domain; (<b>c</b>) manual re-design of optimized geometry.</p> Full article ">Figure 6
<p>Basic principle of the TFP process.</p> Full article ">Figure 7
<p>The composition of the load-compatible fiber paths of the geometry. (<b>a</b>) Design evolution 1: Concept, 2: Generated pattern, 3: Manual adjustments, 4: Final geometry; (<b>b</b>) fiber volume laminate structure.</p> Full article ">Figure 8
<p>Fabrication with 4-head embroidery Tajima TFP machine, provided by IFB.</p> Full article ">Figure 9
<p>Mold and laminate preparation using airtight sealing bags, resin infusion and vacuuming 292 of stapled laminate layers, demolding at IFB (counterclockwise from top left to bottom right).</p> Full article ">Figure 10
<p>Final geometry—Form follows force: (<b>a</b>) Optimized TFP-Pattern for load absorption; (<b>b</b>) three laminates with load depending thickness contribution.</p> Full article ">Figure 11
<p>Shape and laminate composition of the structure, close-up of the surface characteristics (counterclockwise from top left to bottom right).</p> Full article ">
13 pages, 3341 KiB  
Article
Electrical Conductivity Based Ammonia Sensing Properties of Polypyrrole/MoS2 Nanocomposite
by Sharique Ahmad, Imran Khan, Ahmad Husain, Anish Khan and Abdullah M. Asiri
Polymers 2020, 12(12), 3047; https://doi.org/10.3390/polym12123047 - 18 Dec 2020
Cited by 84 | Viewed by 4278
Abstract
Polypyrrole (PPy) and Polypyrrole/MoS2 (PPy/MoS2) nanocomposites were successfully prepared, characterized and studied for ammonia sensing properties. The as-prepared PPy and PPy/MoS2 nanocomposites were confirmed by FTIR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), SEM (scanning electron microscopy) and TEM [...] Read more.
Polypyrrole (PPy) and Polypyrrole/MoS2 (PPy/MoS2) nanocomposites were successfully prepared, characterized and studied for ammonia sensing properties. The as-prepared PPy and PPy/MoS2 nanocomposites were confirmed by FTIR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), SEM (scanning electron microscopy) and TEM (transmission electron microscopy) techniques. The ammonia sensing properties of PPy and PPy/MoS2 nanocomposites were studied in terms of change in DC electrical conductivity on exposure to ammonia vapors followed by ambient air at room temperature. It was observed that the incorporation of MoS2 in PPy showed high sensitivity, significant stability and excellent reversibility. The enhanced sensing properties of PPy/MoS2 nanocomposites could be attributed to comparatively high surface area, appropriate sensing channels and efficiently available active sites. The sensing mechanism is explained on the basis of simple acid-base chemistry of polypyrrole. Full article
(This article belongs to the Special Issue Conducting Polymer-Based Hybrid Nanomaterials)
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<p>The Fourier transform infrared (FTIR) spectra of: (<b>a</b>) PPy, (<b>b</b>) MoS<sub>2</sub> and (<b>c</b>) PPy/MoS<sub>2</sub>.</p> Full article ">Figure 2
<p>The X-ray diffraction (XRD) spectra of: (<b>a</b>) PPy, (<b>b</b>) MoS<sub>2</sub> and (<b>c</b>) PPy/MoS<sub>2</sub>.</p> Full article ">Figure 3
<p>Scanning electron microscopy (SEM) micrographs of: (<b>a</b>) PPy, (<b>b</b>) MoS<sub>2</sub> (<b>c</b>) PPy/MoS<sub>2</sub> and (<b>d</b>) transmission electron microscopy (TEM) micrograph of PPy/MoS<sub>2</sub>.</p> Full article ">Figure 4
<p>Ammonia sensor unit by the four in-line probes method.</p> Full article ">Figure 5
<p>Initial DC electrical conductivities of MoS<sub>2</sub>, PPy and PPy/MoS<sub>2</sub> nanocomposites.</p> Full article ">Figure 6
<p>Effect on the DC electrical conductivity of (<b>a</b>) PPy and (<b>b</b>) PPy/MoS<sub>2</sub> nanocomposites upon exposure to (1000 ppm) ammonia vapors followed by exposure to ambient air with respect to time.</p> Full article ">Figure 7
<p>Effect on the DC electrical conductivity of the PPy/MoS<sub>2</sub> nanocomposites upon exposure to ammonia vapors at different concentrations.</p> Full article ">Figure 8
<p>Electrical conductivity of curve A PPy/MoS<sub>2</sub> nanocomposite and curve B PPy upon alternate exposure to 1000 ppm of ammonia vapors and air with respect to time.</p> Full article ">Figure 9
<p>Selectivity of PPy/MoS<sub>2</sub> nanocomposite toward 1000 ppm of ammonia against different 1 M VOCs.</p> Full article ">Figure 10
<p>Schematic representation of the plausible NH<sub>3</sub> adsorption-desorption sensing mechanism on (<b>a</b>) polypyrrole (PPy) and (<b>b</b>) Polypyrrole/MoS<sub>2</sub> (PPy/MoS<sub>2</sub>) nanocomposites.</p> Full article ">
21 pages, 5281 KiB  
Article
New Insight into the Mechanism of Drug Release from Poly(d,l-lactide) Film by Electron Paramagnetic Resonance
by Natalia A. Chumakova, Elena N. Golubeva, Sergei V. Kuzin, Tatiana A. Ivanova, Igor A. Grigoriev, Sergey V. Kostjuk and Mikhail Ya. Melnikov
Polymers 2020, 12(12), 3046; https://doi.org/10.3390/polym12123046 - 18 Dec 2020
Cited by 10 | Viewed by 2916
Abstract
A novel approach based on convolution of the electron paramagnetic resonance (EPR) spectra was used for quantitative study of the release kinetics of paramagnetic dopants from poly(d,l-lactide) films. A non-monotonic dependence of the release rate on time was reliably [...] Read more.
A novel approach based on convolution of the electron paramagnetic resonance (EPR) spectra was used for quantitative study of the release kinetics of paramagnetic dopants from poly(d,l-lactide) films. A non-monotonic dependence of the release rate on time was reliably recorded. The release regularities were compared with the dynamics of polymer structure changes determined by EPR, SEM, and optic microscopy. The data obtained allow for the conclusion that the main factor governing dopant release is the formation of pores connected with the surface. In contrast, the contribution of the dopant diffusion through the polymer matrix is negligible. The dopant release can be divided into two phases: release through surface pores, which are partially closed with time, and release through pores initially formed inside the polymer matrix due to autocatalytic hydrolysis of the polymer and gradually connected to the surface of the sample. For some time, these processes co-occur. The mathematical model of the release kinetics based on pore formation is presented, describing the kinetics of release of various dopants from the polymer films of different thicknesses. Full article
(This article belongs to the Special Issue Bioactive Polymer Scaffolds and Thin Films for Biomedical Applications: State-of-the-Art and Challenges)
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<p>The structures of the paramagnetic compounds.</p> Full article ">Figure 2
<p>Electron paramagnetic resonance (EPR) spectrum of a liquid probe containing 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxide (TEMPOL) (<b>a</b>), the spectrum of TEMPOL in PBS (<b>b</b>), and the result of their convolution (<b>c</b>).</p> Full article ">Figure 3
<p>The EPR spectrum of 4-oxo-2,2,6,6-tetramethylpiperidine-1-oxide (TEMPONE) in swollen poly(<span class="html-small-caps">d</span>,<span class="html-small-caps">l</span>-lactide) film (<b>a</b>) and the absolute value of its Fourier image (<b>b</b>): the periodic pattern corresponds to the narrow triplet signal.</p> Full article ">Figure 4
<p>SEM images of dry 200 μm poly(<span class="html-small-caps">d</span>,<span class="html-small-caps">l</span>-lactide) (PDL) 02 film: surface (<b>left</b>) and chip (<b>right</b>).</p> Full article ">Figure 5
<p>EPR spectra of TEMPOL in PBS at 298 K (<b>a</b>) and in PDL 02 at 298 K (<b>b</b>) and 100 K (<b>c</b>).</p> Full article ">Figure 6
<p>Kinetic curves corresponding to the release of TEMPOL (black and red symbols) and ATI (blue symbols) from PDL 02 films (<b>a</b>) and of sl-DCF (black symbols) and TEMPONE (red symbols) from PDL 04 films (<b>b</b>) into PBS: measurement errors are 10–12%. The lines are not the result of fitting.</p> Full article ">Figure 7
<p>The EPR spectra of TEMPOL in PDL 02 film recorded at various holding times of the sample in solution: (<b>a</b>) dry sample (black line), 30 min (red line), 1 h (green line), and 6 h (blue line); (<b>b</b>) dry sample (black line), 2 days (red line), 7 days (blue line), and 17 days (green line).</p> Full article ">Figure 8
<p>pH dependence of the distance between the central and left components (ΔB) of the EPR spectra of DPI in water solution.</p> Full article ">Figure 9
<p>Time dependences of the swelling index (SI, black symbols, measurement errors are 5–7%) and of the part of radicals, localized in pores (PR, blue symbols, measurement errors are 10–12%) for TEMPOL in PDL 02 film (<b>a</b>) and for TEMPONE in PDL 04 film (<b>b</b>): the lines are not the results of fitting.</p> Full article ">Figure 10
<p>Optical microphotographs of PDL 04 film recorded after 3 weeks of keeping in PBS.</p> Full article ">Figure 11
<p>SEM microphotographs of PDL 02 (<b>a</b>–<b>f</b>) and PDL 04 (<b>g</b>–<b>k</b>) films recorded after different time of keeping them in PBS: (<b>a</b>)—dry film, (<b>b</b>)—2 h, (<b>c</b>)—4 days, (<b>d</b>)—6 days, (<b>e</b>)—9 days, (<b>f</b>)—11 days, (<b>g</b>)—1 day, (<b>h</b>)—5 days, (<b>i</b>)—90 days, and (<b>j</b>,<b>k</b>)—101 days.</p> Full article ">Figure 12
<p>The kinetic curves of the radical’s decomposition inside PDLLA films in the presence and in the absence of AA in the outer liquid: systems “TEMPONE/PBS + AA” (black symbols), “sl-DCF/PBS + AA” (red symbols), “TEMPONE/PBS” (blue symbols), and “sl-DCF/PBS” (green symbols). Measurement errors are 10–12%.</p> Full article ">Figure 13
<p>Differential kinetic curves for the dopants release from PDL 02 films: TEMPOL/200 μm films (black and red symbols) and ATI/200 μm film (blue symbols) (<b>a</b>), and TEMPOL/50 μm film (<b>b</b>). The lines are the result of polynomial fitting.</p> Full article ">Figure 14
<p>Experimental differential curves (black lines) and corresponding numerical modeling of TEMPOL (<b>a</b>) and ATI (<b>b</b>) release from 200 μm films and of TEMPOL (<b>c</b>) release from 50 μm film: the red lines are the results of modeling, and green and blue lines are contributions of the dopant release through the pores formed at the first and the second stages of pore formation, respectively (see text).</p> Full article ">Figure 15
<p>Experimental cumulative curves (dots) and corresponding numerical modeling (lines) of TEMPOL (<b>a</b>) and ATI (<b>b</b>) release from 200 μm PDLLA films and of TEMPOL (<b>c</b>) release from 50 μm film.</p> Full article ">Figure 15 Cont.
<p>Experimental cumulative curves (dots) and corresponding numerical modeling (lines) of TEMPOL (<b>a</b>) and ATI (<b>b</b>) release from 200 μm PDLLA films and of TEMPOL (<b>c</b>) release from 50 μm film.</p> Full article ">
12 pages, 2685 KiB  
Article
The Potential of Polyethylene Terephthalate Glycol as Biomaterial for Bone Tissue Engineering
by Mohamed H. Hassan, Abdalla M. Omar, Evangelos Daskalakis, Yanhao Hou, Boyang Huang, Ilya Strashnov, Bruce D. Grieve and Paulo Bártolo
Polymers 2020, 12(12), 3045; https://doi.org/10.3390/polym12123045 - 18 Dec 2020
Cited by 44 | Viewed by 4922
Abstract
The search for materials with improved mechanical and biological properties is a major challenge in tissue engineering. This paper investigates, for the first time, the use of Polyethylene Terephthalate Glycol (PETG), a glycol-modified class of Polyethylene Terephthalate (PET), as a potential material for [...] Read more.
The search for materials with improved mechanical and biological properties is a major challenge in tissue engineering. This paper investigates, for the first time, the use of Polyethylene Terephthalate Glycol (PETG), a glycol-modified class of Polyethylene Terephthalate (PET), as a potential material for the fabrication of bone scaffolds. PETG scaffolds with a 0/90 lay-dawn pattern and different pore sizes (300, 350 and 450 µm) were produced using a filament-based extrusion additive manufacturing system and mechanically and biologically characterized. The performance of PETG scaffolds with 300 µm of pore size was compared with polycaprolactone (PCL). Results show that PETG scaffolds present significantly higher mechanical properties than PCL scaffolds, providing a biomechanical environment that promotes high cell attachment and proliferation. Full article
(This article belongs to the Special Issue 3D Bioprinting and Medical Applications)
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<p>The Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) spectrum of Polyethylene terephthalate glycol modified (PETG). Its characteristic repeated units are highlighted: 192.8 g/mol for the Terephthalic acid + Ethylene Glycol (TPA + EG) unit and 274.3 g/mol for Terephthalic acid + Cyclohexanedimethanol (TPA + CHDM).</p> Full article ">Figure 2
<p>(<b>A</b>) Top view of a polycaprolactone (PCL) scaffold, (<b>B</b>) cross-section view of a PCL scaffold, (<b>C</b>) top view of a Polyethylene terephthalate glycol modified (PETG) scaffold, (<b>D</b>) cross-section view of a Polyethylene terephthalate glycol modified (PETG) scaffold. All scaffolds were designed considering a pore size of 350 µm.</p> Full article ">Figure 3
<p>Stress vs. strain curves for PCL scaffolds and PETG scaffolds with different pore sizes.</p> Full article ">Figure 4
<p>Compression modulus for the PCL scaffold and PETG scaffolds with different pore size. *** <span class="html-italic">p</span> &lt; 0.001 compared with control (PCL), <sup>##</sup> <span class="html-italic">p</span> &lt; 0.01 and <sup>###</sup> <span class="html-italic">p</span> &lt; 0.001 compared with different pore size. The *** Statistical evidence (<span class="html-italic">p</span> &lt; 0.001) is the one-way analysis of the mechanical compression test with the use of GraphPad Prism software and it is used to show the difference be-tween the results. The * is small difference and while more * are added the differences between the results are higher. * compared with PCL scaffolds, # compared with different pore size of PETG scaffolds.</p> Full article ">Figure 5
<p>Compression strength values for the PCL scaffold and PETG scaffolds with different pore size. *** <span class="html-italic">p</span> &lt; 0.001 compared with control (PCL), <sup>##</sup> <span class="html-italic">p</span> &lt; 0.01 and <sup>###</sup> <span class="html-italic">p</span> &lt; 0.001 compared with different pore size. The *** Statistical evidence (<span class="html-italic">p</span> &lt; 0.001) is the one-way analysis of the mechanical compression test with the use of GraphPad Prism software and it is used to show the difference be-tween the results. The * is small difference and while more * are added the differences between the results are higher. * compared with PCL scaffolds, # compared with different pore size of PETG scaffolds.</p> Full article ">Figure 6
<p>Alamar Blue results for both PCL and PETG scaffolds at days 1, 7 and 14 post-cell-seeding. * Statistical evidence (<span class="html-italic">p</span> &lt; 0.05) analyzed by one-way analysis of variance (ANOVA) and Tukey’s post-test. The * Statistical evidence (<span class="html-italic">p</span> &lt; 0.05), **, *** is the one-way analysis of variance (one-way ANOVA) and Tukey’s post hoc test with the use of GraphPad Prism software and it is used to show the difference be-tween the results. The * is small difference and while more * are added the differences between the results are higher.</p> Full article ">Figure 7
<p>Cells on PETG-350 scaffolds after 14 days of cell seeding. (<b>A</b>) Top view image of the PETG scaffold, (<b>B</b>) cross-section image of PETG scaffold, (<b>C</b>) magnified image showing cells covering the PETG filament, (<b>D</b>) cells bridging adjacent layers.</p> Full article ">
13 pages, 2811 KiB  
Article
Polyethylene Glycol 35 (PEG35) Modulates Exosomal Uptake and Function
by Ana Ferrero-Andrés, Daniel Closa, Joan Roselló-Catafau and Emma Folch-Puy
Polymers 2020, 12(12), 3044; https://doi.org/10.3390/polym12123044 - 18 Dec 2020
Cited by 6 | Viewed by 2631
Abstract
Polyethylene glycols (PEGs) are neutral polymers widely used in biomedical applications due to its hydrophilicity and biocompatibility. Exosomes are small vesicles secreted by nearly all cell types and play an important role in normal and pathological conditions. The purpose of this study was [...] Read more.
Polyethylene glycols (PEGs) are neutral polymers widely used in biomedical applications due to its hydrophilicity and biocompatibility. Exosomes are small vesicles secreted by nearly all cell types and play an important role in normal and pathological conditions. The purpose of this study was to evaluate the role of a 35-kDa molecular weight PEG (PEG35) on the modulation of exosome-mediated inflammation. Human macrophage-like cells THP-1, epithelial BICR-18, and CAPAN-2 cells were exposed to PEG35 prior to incubation with exosomes of different cellular origins. Exosome internalization was evaluated by confocal microscopy and flow cytometry. In another set of experiments, macrophages were treated with increasing concentrations of PEG35 prior to exposure with the appropriate stimuli: lipopolysaccharide, BICR-18-derived exosomes, or exosomes from acute pancreatitis-induced rats. Nuclear Factor Kappa B (NFκB) and Signal transducer and activator of transcription 3 (STAT3) activation and the expression levels of pro-inflammatory Interleukin 1β (IL1β) were determined. PEG35 administration significantly enhanced the internalization of exosomes in both macrophages and epithelial cells. Further, PEG35 ameliorated the inflammatory response induced by acute pancreatitis-derived exosomes by reducing the expression of IL1β and p65 nuclear translocation. Our results revealed that PEG35 promotes the cellular uptake of exosomes and modulates the pro-inflammatory effect of acute pancreatitis-derived vesicles through inhibition of NFκB, thus emphasizing the potential value of PEG35 as an anti-inflammatory agent for biomedical purposes. Full article
(This article belongs to the Section Polymer Applications)
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<p>Characterization of extracellular vesicles: (<b>a</b>) Size distribution curves, evaluated by NanoSight, indicated that sizes are compatible with exosomes. (<b>b</b>) Western blot analysis was performed with whole cell lysates (CL) and pooled exosomes isolated from plasmatic acute pancreatitis-induced rats (ExoAP) and from epithelial cell line BICR-18 (ExoB) to confirm the presence of classical exosome marker (TSG101) and the absence of endoplasmic reticulum contamination (calnexin). ExoAP, exosomes from the plasma of acute pancreatitis-induced rats; CL, cell lysates; and ExoB, exosomes from BICR-18.</p> Full article ">Figure 2
<p>PEG35-enhanced uptake of exosomes by THP-1 macrophages: (<b>a</b>) representative confocal microscopy images showing internalized PKH26-labelled ExoB by THP-1 macrophages subjected to 4% PEG35 treatment; (<b>b</b>) fluorescence intensity analysis of the PKH26-labelled ExoB; (<b>c</b>) representative confocal microscopy images showing internalization of PKH26-labelled ExoAP by macrophages incubated with 4% PEG35; (<b>d</b>) fluorescence intensity analysis of the PKH26-labelled ExoAP, with Untreated and PEG35-treated cells fixed and imaged with confocal microscopy (scale bar, 20 µm; blue, DAPI stained nuclei; and red, PKH26 stained exosomes); (<b>e</b>) flow cytometry quantification of internalized PKH26-labeled ExoAP by macrophages at increasing concentrations of PEG35; (<b>f</b>) Median Fluorescence Intensity (MFI) normalized to the ExoAP group; and (<b>g</b>) confocal microscopy images of internalized exosomes by macrophages (z-stack projection) with orthogonal cross sections (x and y directions). Up, THP-1 macrophages incubated with exosomes; down, THP-1 macrophages pretreated with PEG35 and co-incubated with exosomes; and scale bar, 10 µm. Nuclei are reported in blue (DAPI), exosomes are in red (PKH26), and membranes are in green (PKH67). The values shown represent the mean ± SEM. * <span class="html-italic">p</span> &lt; 0.05 versus ExoB or ExoAP. PEG35, 35-kDa polyethylene glycol; ExoB, exosomes from BICR-18 cells; ExoAP, exosomes from AP-induced rats; and MFI, Median Fluorescence Intensity.</p> Full article ">Figure 3
<p>PEG35 enhanced the uptake of exosomes by epithelial cells. (<b>a</b>) Representative images showing internalized ExoB by epithelial BICR-18 and CAPAN-2 cells under treatment with 4% PEG35: untreated and PEG35-treated cells were fixed and then were imaged with confocal microscopy (scale bar, 20 µm; blue, DAPI stained nuclei; and red, PKH26 stained exosomes). (<b>b</b>) Fluorescence intensity analysis of the PKH26-labelled exosomes: the values shown represent the mean ± SEM. * <span class="html-italic">p</span> &lt; 0.05 versus ExoB. Data is representative of several repeated experiments. ExoB, exosomes from BICR-18 cells; PEG35, 35-kDa polyethylene glycol.</p> Full article ">Figure 4
<p>Expression of pro-inflammatory Interleukin 1β (IL1β) in THP-1-treated cells: (<b>a</b>) Gene expression by real-time qRT-PCR of IL1β in THP-1 macrophages treated with increasing concentrations of ExoAP; (<b>b</b>) gene expression by real-time qRT-PCR of IL1β by THP-1 cells subjected to increasing concentrations of PEG35 and co-incubated with ExoAP; (<b>c</b>) IL1β gene expression by real-time qRT-PCR in THP-1 macrophages subjected to increasing concentrations of PEG35 and co-incubated with lipopolysaccharide (LPS), where, in all cases, mRNA induction levels were normalized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA expression; and (<b>d</b>) expression levels of IL1β protein released by THP-1 cells pretreated with increasing concentrations of PEG35 and then co-incubated with LPS. Bars represent the mean values of each group ± SEM. * <span class="html-italic">p</span> &lt; 0.05 versus control, + <span class="html-italic">p</span> &lt; 0.05 versus ExoAP or LPS. Each determination was carried out in triplicate. ExoAP, exosomes from acute-pancreatitis-induced rats; LPS, lipopolysaccharide; PEG35, 35-kDa polyethylene glycol; and IL1β, interleukin 1β.</p> Full article ">Figure 5
<p>PEG35 suppressed p65 translocation to the nucleus in LPS or ExoAP-stimulated macrophages: (<b>a</b>) representative images of immunofluorescence staining for subcellular localization of the p65 subunit of Nuclear Factor Kappa B (NFκB) and Signal transducer and activator of transcription 3 (STAT3) observed by confocal microscopy, with scale bar 20 µm, and (<b>b</b>) nuclear expression of p65 assessed by Western blot analysis. TBP expression was used as the loading control. Densitometry quantification of the Western blot was performed for p65. Data are representative of several repeated experiments. LPS, lipopolysaccharide; ExoAP, exosomes from AP-induced rats; PEG35, 35-kDa polyethylene glycol; and TBP, TATA binding protein.</p> Full article ">
13 pages, 3689 KiB  
Article
Dope-Dyeing of Polyvinyl Alcohol (PVA) Nanofibres with Remazol Yellow FG
by Fatirah Fadil, Farah Atiqah Adli, Nor Dalila Nor Affandi, Ahmad Mukifza Harun and Mohammad Khursheed Alam
Polymers 2020, 12(12), 3043; https://doi.org/10.3390/polym12123043 - 18 Dec 2020
Cited by 15 | Viewed by 3803
Abstract
The lack of aesthetic properties of electrospun nanofibres in terms of colour appearance is the drive in this preliminary study. This research is conducted to study the dyeing behaviour and colorimetric properties of electrospun nanofibres blended with Remazol Yellow FG reactive dye using [...] Read more.
The lack of aesthetic properties of electrospun nanofibres in terms of colour appearance is the drive in this preliminary study. This research is conducted to study the dyeing behaviour and colorimetric properties of electrospun nanofibres blended with Remazol Yellow FG reactive dye using dope-dyeing method via electrospinning process. This paper reports the colorimetric properties of dyed poly vinyl alcohol (PVA) nanofibres within the range of 2.5 wt.% to 12.5 wt.% dye content. The electrospinning parameters were fixed at the electrospinning distance of 10 cm, constant feed rate of 0.5 mL/h and applied voltage of 15 kV. The resulting impregnated dye of 10 wt.% exhibits acceptable colour difference of dyed PVA nanofibres, with a mean fibre diameter of 177.1 ± 11.5 nm. The SEM micrographs show the effect of dye content on morphology and fibre diameter upon the increment of dye used. Further increase of dye content adversely affects the jet stability during the electrospinning, resulting in macroscopic dropping phenomenon. The presence of all prominent peaks of Remazol dye in the PVA nanofibers was supported with FTIR analysis. The addition of dye into the nanofibres has resulted in the enhancement of thermal stability of the PVA as demonstrated by TGA analysis. Full article
(This article belongs to the Special Issue Polymeric Synthetic Fibres)
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<p>Chemical structure of Remazol Yellow FG.</p> Full article ">Figure 2
<p>Illustration of dope-dyeing PVA nanofibres throughout electrospinning.</p> Full article ">Figure 3
<p>SEM micrographs of (<b>a</b>) control PVA (<b>b</b>) 2.5 wt.% (<b>c</b>) 5.0 wt.% (<b>d</b>) 7.5 wt.% (<b>e</b>) 10.0 wt.% (<b>f</b>) 12.5 wt.% of dyed PVA nanofibres using Remazol FG yellow dye.</p> Full article ">Figure 4
<p>SEM micrographs of (<b>a</b>) 0.2 wt.% (<b>b</b>) 0.4 wt.% (<b>c</b>) 0.6 wt.% (<b>d</b>) 0.8 wt.% (<b>e</b>) 1.0 wt.% of dyed PVA nanofibers using Ase Direct Supra Red BWS dye.</p> Full article ">Figure 5
<p>FTIR ATR spectra of (<b>a</b>) Remazol Yellow FG dye and (<b>b</b>) dyed PVA nanofibres.</p> Full article ">Figure 6
<p>TGA thermogram of (<b>a</b>) PVA (<b>b</b>) dyed PVA electrospun nanofibres.</p> Full article ">Figure 6 Cont.
<p>TGA thermogram of (<b>a</b>) PVA (<b>b</b>) dyed PVA electrospun nanofibres.</p> Full article ">Figure 7
<p>UV-Visible spectra of Remazol Yellow FG solution and in vitro release of Remazol Yellow FG supernatant originated from dyed electrospun nanofibres. The inset shows the zoom-in UV-Visible spectra of dyed electrospun nanofibres.</p> Full article ">Figure 8
<p>Fluorescence emission spectra of Remazol Yellow FG dyed PVA nanofibres.</p> Full article ">Figure 9
<p>Schematic illustration of the proposed mechanism of dye-polymer interaction.</p> Full article ">
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