Conference paper presented at European Congress and Exhibition on Advanced Materials and Processe... more Conference paper presented at European Congress and Exhibition on Advanced Materials and Processes (EUROMAT 2013), which took place in Sevilla (Spain) during 8-13th September 2013.
Journal of Materials in Civil Engineering, Oct 1, 2017
AbstractAn acrylamide-based chemical grouting system has been developed that allows users to init... more AbstractAn acrylamide-based chemical grouting system has been developed that allows users to initiate the curing process on demand. After heating a localized area, the curing reaction propagates th...
We demonstrate thiol-acrylate microfluidics prepared via soft lithography for single-step protein... more We demonstrate thiol-acrylate microfluidics prepared via soft lithography for single-step protein immobilization and fluorescence-based pathogen detection. Such microfluidics are formed via room temperature curing, and bonded without oxygen plasma. The background fluorescence of the resin was found to be similar to PDMS for several filter sets. We also show that thiol-acrylate devices are able to bond to gold-coated surfaces, which allows for integration with microfabricated sensors.
These sytems are advantageous in that they require only an initial stimulus of energy, allow a ra... more These sytems are advantageous in that they require only an initial stimulus of energy, allow a rapid conversion of monomer to polymer, and have very little residual waste. However, the shelf life of the initiator in monomer solution has often been a disadvantage to the applicability of frontal polymerization. The issue of pot life has been addressed through the encapsulation of the initiator. 2 The capsules produced in this study contain a cumene hydroperoxide-core surrounded by a polyurea shell. The capsule shells are formed via interfacial polymerization between an isocyanate and an amine. Amine functionality can be used to control the degree of crosslinking and subsequently the stability of the polymer shell. This study focuses on the effect of a varying amine functionality on capsule stability, using amines such as ethylene diamine and tetraethylene pentamine. The effects of isocyante to primary amine ratio on polyurea shell stability are also being studied. Experimental Materials. Cumene hydroperoxide (Aldrich) was used as the initiator core. The shell components in the interfacial polymerization process consist of Mondur MRS (a mixture of polyfunctional isocyanates supplied from Bayer), ethylene diamine (99% technical grade) and tetraethylene pentamine (TEPA) (Aldrich). Polyvinyl alcohol (Aldrich) was used as an emulsifier in the interfacial polymerization process. 1,6 hexanedioldiacrylate (80%, technical grade) (HDDA) was obtained from UCB. Cobalt naphthenate in mineral spirits (8% cobalt) (Aldrich) was used as a redox accelerator in frontal polymerization systems. Procedure. A core solution was prepared by dissolving 80 mL of cumene hydroperoxide in 10 mL of Mondur MRS. The core solution was then emulsified in 250 mL of a 1.2% PVA solution with a stir motor equipped with a 3 bladed propeller. Droplets of the core material, ranging from 150– 300 microns in diameter, were achieved by stirring the emulsion at 230 rpm for approximately 2 minutes. A solution of 8.55 mL of TEPA in 20 mL of deionized water was added to the emulsion and placed in a water bath at 50 °C. The solution was allowed to react at 50 °C for 4 hours with continuous mixing at 230 rpm. The capsules were filtered by vacuum filtration leaving a microcapsule cake that was separated using fumed silica. The microcapsules were allowed to dry overnight. The capsules were composed of approximately 58% Cumene hydroperoxide by weight. They were washed with heptane to remove any residual initiator from the outside of the shell before adding to the frontal polymerization system. All frontal polymerization experiments were performed in glass test tubes, 16 x 125 mm (VWR #72690-022) with a plastic screw cap (VWR #60826-290) attached. A soldering iron was used to thermally initiate polymerization from the top of the test tube. Fronts were performed in HDDA systems containing 2% v/v of the encapsulated cumene hydroperoxide. The reaction medium contained 4% w/v silica gel to prevent the capsule from settling out. Front velocities were determined for systems containing capsules prepared with varying isocyanate to primary amine ratios. The pot life of the microcapsules in monomer solution was also tested. The systems were stored under various conditions and their front velocities measured at different storage time intervals. . Results and Discussion Of all capsules produced, those containing diamine as a shell component had the lowest weight percent, with a core loading weight percentage of 28%. The low core loading percentage is a result of a lower degree of crosslinking due to the presence of fewer crosslinking secondary amine groups. The capsules produced using pentamine as a shell component averaged a core loading percentage of 60%. However, this is lower than the core loading percentage of capsules produced using tetramines and triamines as shell components. The decrease in capsule stability is most likely due to intercapsule crosslinking caused by an increase in secondary amine functionality. All systems studied exhibited constant front velocities, seen in Figure 1. Figure 1 Plot of position versus time for the frontal polymerization of HDDA using 2% v/v CHP (encapsulated). The front velocities for the systems studied are slower than those containing unencapsulated initiators because the initiator must first release from the shell before it can react with the monomer solution. Also, the capsules act as a filler causing an increase in viscosity and a slight reduction in the front temperature, resulting in a decreased front velocity. Studies have shown that systems containing encapsulated initiators have a longer pot life than those containing unencapsulated initiators. 2
Many of the most remarkable achievements of chemical science involve either synthesis (the design... more Many of the most remarkable achievements of chemical science involve either synthesis (the design and construction of molecules) or analysis (the identification and structural characterization of molecules). We have organized our discussion of oscillating reactions along similar lines. In the previous chapter, we described how chemists have learned to build chemical oscillators. Now, we will consider how to dissect an oscillatory reaction into its component parts—the question of mechanism. A persuasive argument can be made that it was progress in unraveling the mechanism of the prototype BZ reaction in the 1970s that gave the study of chemical oscillators the scientific respectability that had been denied it since the discovery of the earliest oscillating reactions. The formulation by Field, Körös, and Noyes (Field et al., 1972) of a set of chemically and thermodynamically plausible elementary steps consistent with the observed “exotic” behavior of an acidic solution of bromate and ...
Frontal polymerization is a process in which a localized reaction zone propagates from the coupli... more Frontal polymerization is a process in which a localized reaction zone propagates from the coupling of thermal transport and the Arrhenius rate dependence of an exothermic polymerization; monomer is converted into polymer as the front passes through an unstirred medium. Herein we report the first study of charge transfer complexes (CTCs) as photo/thermal initiators for free‐radical frontal polymerization. Front velocity was studied as a function of mole ratio between an aromatic amine, such as dimethyl‐p‐toluidine or dimethylaniline, and an iodonium salt. It was found that the front velocity reached a maximum at a certain mole ratio of amine to iodonium salt. The velocity remained constant upon increasing the ratio of amine to iodonium salt past this critical ratio. Fronts were also studied using N‐phenyl glycine as an electron donor, but its utility was limited by low solubility. Lastly, the steric and electronic effects of the iodonium salt and counter anion were explored. It was ...
Chaos: An Interdisciplinary Journal of Nonlinear Science, 2022
This work investigates experimentally and numerically frontal polymerization in a thermally aniso... more This work investigates experimentally and numerically frontal polymerization in a thermally anisotropic system with parallel copper strips embedded in 1,6-hexanediol diacrylate resin. Both experiments and multiphysics finite element analyses reveal that the front propagation in the thermally anisotropic system is orientation-dependent, leading to variations in the front shape and the front velocity due to the different front–metal strip interaction mechanisms along and across the metal strips. The parameters entering the cure kinetics model used in this work are chosen to capture the key characteristics of the polymerization front, i.e., the front temperature and velocity. Numerical parametric analyses demonstrate that the front velocity in the directions parallel and perpendicular to the metal strips increases as the system size decreases and approaches the analytical prediction for homogenized systems. A two-dimensional homogenized model for anisotropic frontal polymerization in t...
John Pojman of the chemistry department at Louisiana State University joins us to discuss his ama... more John Pojman of the chemistry department at Louisiana State University joins us to discuss his amazing collection of pocket protectors and other peculiarities of the nerd class
The purpose of this study is to develop a novel bone replacement using in situ polymerization of ... more The purpose of this study is to develop a novel bone replacement using in situ polymerization of thiol-acrylate with adipose tissue derived adult stem cells (ASCs). Specifically, Poly(ethylene glycol) diacrylate-co-trimethylolpropane tris (3-mercaptopropionate) (PEGDA-co-TMPTMP) was synthesized with 10% Hydroxyapatite (HA) foam by an amine-catalyzed Michael addition reaction. Initial characterization studies were performed to determine the temperature profile during the exothermic reaction showing a peak temperature of 50°C. To prevent hyperthermic cell damage and death during the exothermic polymerization procedure, the hASCs were encapsulated in alginate. Characterization of the 3-D structure and interconnectivity of pores in the polymeric foam scaffolds were performed using FIB-SEM and Micro-CT showing uniform distribution of HA. Cell viability experiments within the polymeric scaffold were performed using Vybrant® MTT cell profileration method, as well as fluorescent dyes: Calce...
Conference paper presented at European Congress and Exhibition on Advanced Materials and Processe... more Conference paper presented at European Congress and Exhibition on Advanced Materials and Processes (EUROMAT 2013), which took place in Sevilla (Spain) during 8-13th September 2013.
Journal of Materials in Civil Engineering, Oct 1, 2017
AbstractAn acrylamide-based chemical grouting system has been developed that allows users to init... more AbstractAn acrylamide-based chemical grouting system has been developed that allows users to initiate the curing process on demand. After heating a localized area, the curing reaction propagates th...
We demonstrate thiol-acrylate microfluidics prepared via soft lithography for single-step protein... more We demonstrate thiol-acrylate microfluidics prepared via soft lithography for single-step protein immobilization and fluorescence-based pathogen detection. Such microfluidics are formed via room temperature curing, and bonded without oxygen plasma. The background fluorescence of the resin was found to be similar to PDMS for several filter sets. We also show that thiol-acrylate devices are able to bond to gold-coated surfaces, which allows for integration with microfabricated sensors.
These sytems are advantageous in that they require only an initial stimulus of energy, allow a ra... more These sytems are advantageous in that they require only an initial stimulus of energy, allow a rapid conversion of monomer to polymer, and have very little residual waste. However, the shelf life of the initiator in monomer solution has often been a disadvantage to the applicability of frontal polymerization. The issue of pot life has been addressed through the encapsulation of the initiator. 2 The capsules produced in this study contain a cumene hydroperoxide-core surrounded by a polyurea shell. The capsule shells are formed via interfacial polymerization between an isocyanate and an amine. Amine functionality can be used to control the degree of crosslinking and subsequently the stability of the polymer shell. This study focuses on the effect of a varying amine functionality on capsule stability, using amines such as ethylene diamine and tetraethylene pentamine. The effects of isocyante to primary amine ratio on polyurea shell stability are also being studied. Experimental Materials. Cumene hydroperoxide (Aldrich) was used as the initiator core. The shell components in the interfacial polymerization process consist of Mondur MRS (a mixture of polyfunctional isocyanates supplied from Bayer), ethylene diamine (99% technical grade) and tetraethylene pentamine (TEPA) (Aldrich). Polyvinyl alcohol (Aldrich) was used as an emulsifier in the interfacial polymerization process. 1,6 hexanedioldiacrylate (80%, technical grade) (HDDA) was obtained from UCB. Cobalt naphthenate in mineral spirits (8% cobalt) (Aldrich) was used as a redox accelerator in frontal polymerization systems. Procedure. A core solution was prepared by dissolving 80 mL of cumene hydroperoxide in 10 mL of Mondur MRS. The core solution was then emulsified in 250 mL of a 1.2% PVA solution with a stir motor equipped with a 3 bladed propeller. Droplets of the core material, ranging from 150– 300 microns in diameter, were achieved by stirring the emulsion at 230 rpm for approximately 2 minutes. A solution of 8.55 mL of TEPA in 20 mL of deionized water was added to the emulsion and placed in a water bath at 50 °C. The solution was allowed to react at 50 °C for 4 hours with continuous mixing at 230 rpm. The capsules were filtered by vacuum filtration leaving a microcapsule cake that was separated using fumed silica. The microcapsules were allowed to dry overnight. The capsules were composed of approximately 58% Cumene hydroperoxide by weight. They were washed with heptane to remove any residual initiator from the outside of the shell before adding to the frontal polymerization system. All frontal polymerization experiments were performed in glass test tubes, 16 x 125 mm (VWR #72690-022) with a plastic screw cap (VWR #60826-290) attached. A soldering iron was used to thermally initiate polymerization from the top of the test tube. Fronts were performed in HDDA systems containing 2% v/v of the encapsulated cumene hydroperoxide. The reaction medium contained 4% w/v silica gel to prevent the capsule from settling out. Front velocities were determined for systems containing capsules prepared with varying isocyanate to primary amine ratios. The pot life of the microcapsules in monomer solution was also tested. The systems were stored under various conditions and their front velocities measured at different storage time intervals. . Results and Discussion Of all capsules produced, those containing diamine as a shell component had the lowest weight percent, with a core loading weight percentage of 28%. The low core loading percentage is a result of a lower degree of crosslinking due to the presence of fewer crosslinking secondary amine groups. The capsules produced using pentamine as a shell component averaged a core loading percentage of 60%. However, this is lower than the core loading percentage of capsules produced using tetramines and triamines as shell components. The decrease in capsule stability is most likely due to intercapsule crosslinking caused by an increase in secondary amine functionality. All systems studied exhibited constant front velocities, seen in Figure 1. Figure 1 Plot of position versus time for the frontal polymerization of HDDA using 2% v/v CHP (encapsulated). The front velocities for the systems studied are slower than those containing unencapsulated initiators because the initiator must first release from the shell before it can react with the monomer solution. Also, the capsules act as a filler causing an increase in viscosity and a slight reduction in the front temperature, resulting in a decreased front velocity. Studies have shown that systems containing encapsulated initiators have a longer pot life than those containing unencapsulated initiators. 2
Many of the most remarkable achievements of chemical science involve either synthesis (the design... more Many of the most remarkable achievements of chemical science involve either synthesis (the design and construction of molecules) or analysis (the identification and structural characterization of molecules). We have organized our discussion of oscillating reactions along similar lines. In the previous chapter, we described how chemists have learned to build chemical oscillators. Now, we will consider how to dissect an oscillatory reaction into its component parts—the question of mechanism. A persuasive argument can be made that it was progress in unraveling the mechanism of the prototype BZ reaction in the 1970s that gave the study of chemical oscillators the scientific respectability that had been denied it since the discovery of the earliest oscillating reactions. The formulation by Field, Körös, and Noyes (Field et al., 1972) of a set of chemically and thermodynamically plausible elementary steps consistent with the observed “exotic” behavior of an acidic solution of bromate and ...
Frontal polymerization is a process in which a localized reaction zone propagates from the coupli... more Frontal polymerization is a process in which a localized reaction zone propagates from the coupling of thermal transport and the Arrhenius rate dependence of an exothermic polymerization; monomer is converted into polymer as the front passes through an unstirred medium. Herein we report the first study of charge transfer complexes (CTCs) as photo/thermal initiators for free‐radical frontal polymerization. Front velocity was studied as a function of mole ratio between an aromatic amine, such as dimethyl‐p‐toluidine or dimethylaniline, and an iodonium salt. It was found that the front velocity reached a maximum at a certain mole ratio of amine to iodonium salt. The velocity remained constant upon increasing the ratio of amine to iodonium salt past this critical ratio. Fronts were also studied using N‐phenyl glycine as an electron donor, but its utility was limited by low solubility. Lastly, the steric and electronic effects of the iodonium salt and counter anion were explored. It was ...
Chaos: An Interdisciplinary Journal of Nonlinear Science, 2022
This work investigates experimentally and numerically frontal polymerization in a thermally aniso... more This work investigates experimentally and numerically frontal polymerization in a thermally anisotropic system with parallel copper strips embedded in 1,6-hexanediol diacrylate resin. Both experiments and multiphysics finite element analyses reveal that the front propagation in the thermally anisotropic system is orientation-dependent, leading to variations in the front shape and the front velocity due to the different front–metal strip interaction mechanisms along and across the metal strips. The parameters entering the cure kinetics model used in this work are chosen to capture the key characteristics of the polymerization front, i.e., the front temperature and velocity. Numerical parametric analyses demonstrate that the front velocity in the directions parallel and perpendicular to the metal strips increases as the system size decreases and approaches the analytical prediction for homogenized systems. A two-dimensional homogenized model for anisotropic frontal polymerization in t...
John Pojman of the chemistry department at Louisiana State University joins us to discuss his ama... more John Pojman of the chemistry department at Louisiana State University joins us to discuss his amazing collection of pocket protectors and other peculiarities of the nerd class
The purpose of this study is to develop a novel bone replacement using in situ polymerization of ... more The purpose of this study is to develop a novel bone replacement using in situ polymerization of thiol-acrylate with adipose tissue derived adult stem cells (ASCs). Specifically, Poly(ethylene glycol) diacrylate-co-trimethylolpropane tris (3-mercaptopropionate) (PEGDA-co-TMPTMP) was synthesized with 10% Hydroxyapatite (HA) foam by an amine-catalyzed Michael addition reaction. Initial characterization studies were performed to determine the temperature profile during the exothermic reaction showing a peak temperature of 50°C. To prevent hyperthermic cell damage and death during the exothermic polymerization procedure, the hASCs were encapsulated in alginate. Characterization of the 3-D structure and interconnectivity of pores in the polymeric foam scaffolds were performed using FIB-SEM and Micro-CT showing uniform distribution of HA. Cell viability experiments within the polymeric scaffold were performed using Vybrant® MTT cell profileration method, as well as fluorescent dyes: Calce...
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