Temperature dependent static dielectric constant and viscosity behaviour of glycerol–amide binary mixtures: Characterization of dominant complex structures in dielectric polarization and viscous flow processes

Journal of Molecular Liquids 154 (2010) 117–123 Contents lists available at ScienceDirect Journal of Molecular Liquids j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m o l l i q Temperature dependent static dielectric constant and viscosity behaviour of glycerol–amide binary mixtures: Characterization of dominant complex structures in dielectric polarization and viscous flow processes R.J. Sengwa ⁎, Vinita Khatri, Shobhna Choudhary, Sonu Sankhla Dielectric Research Laboratory, Department of Physics, J.N.V. University, Jodhpur 342005, India a r t i c l e i n f o Article history: Received 27 March 2010 Accepted 19 April 2010 Available online 24 April 2010 Keywords: Static dielectric constant Molecular interactions Glycerol Amides a b s t r a c t The static dielectric constant and viscosity of the binary mixtures of glycerol (Gly) with N,Ndimethylformamide (DMF) and N,N-dimethylacetamide (DMA) were measured over the entire composition range at temperatures 288.15, 303.15, 318.15 and 333.15 K. The concentration dependent non-linear behaviour of the measured thermodynamical parameters revealed the formation of hydrogen bond interactions between glycerol and amide molecules with a variety of complexes. The excess dielectric constant and excess viscosity were determined and analyzed for the confirmation of the composition of dominant complex species. Results inferred that the dielectric polarization in both the Gly–DMF and Gly– DMA mixtures is governed by 1:1 complex species with enhanced dipolar ordering at all the investigated temperatures. The complex species of 3Gly:DMF and 2Gly:DMA facilitates the viscous flow process in Gly– DMF and Gly–DMA mixtures, respectively and the density of these species is strongly influenced by the change in temperature. Arrhenius type behaviour of viscosity against the reciprocal of temperature was used to determine the apparent activation energy of the viscous flow. The electric-field-induced increment of the Helmholtz free energy and the entropy were determined from the temperature dependence of the static dielectric constant and its derivative of the binary mixtures. Results were discussed to assess the volume effect of DMF and DMA molecules on hydrogen bonding interactions with glycerol molecules in order to confirm the structural conformations of these mixed solvents. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The knowledge of precise values of dielectric constant (relative permittivity) and viscosity as a function of temperature and concentration of the mixed solvents is the general goal of soft materials science, which has attracted considerable attention in last few decades [1–17]. In fact the study of precise values of thermophysical properties such as dielectric constant, viscosity, density, refractive index etc. represent a powerful way for the characterization of molecular interactions, which is complementary to advance infrared and nuclear magnetic resonance techniques. These values provide the confirmation of association phenomena between unlike molecules especially through hydrogen bond (H-bond) interactions and dipole ordering in the liquid mixtures of dipolar solvents [1–27]. The characterization of dielectric constant of mixed solvents is needed for the design of a suitable solvent of required solvating power in view of their pharmaceutical, chemical, analytical and materials science applications, and also in pulse power design technology. ⁎ Corresponding author. Tel.: + 91 291 2720857; fax: + 91 291 2649465. E-mail address: rjsengwa@rediffmail.com (R.J. Sengwa). 0167-7322/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.molliq.2010.04.014 Liquid mixtures containing the amide functional group constitute an important technique in the structural interpretation of complex materials of biological and pharmaceutical interest. Earlier [18–24], we have extensively investigated the dielectric properties of amides mixed with various polar solvents at fixed temperature for understanding the H-bonding molecular interactions between the amides and the solvents. In continuation of our ongoing research work on amides–cosolvents mixtures, in this manuscript, we have undertaken the temperature dependent dielectric constant and viscosity behaviour of glycerol (Gly) mixed with N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) over the entire mixing concentration range. This study aims to explore the dominant Gly–DMF and Gly– DMA complex species that contributed in molecular dielectric polarization and viscous flow processes. The temperature effect on the density of these complex species was examined using their excess dielectric constant and excess viscosity properties. The study of these binary mixtures is interesting because the polar protic Gly and aprotic DMF and DMA have a wide liquid range, high dielectric constant, and a huge difference in their viscosity values. Survey of literature exhibits that so far temperature dependent excess dielectric and viscosity properties of the mixed solvents of broad viscosity difference mixture constituents are not attempted. Numerous studies on mixed solvents 118 R.J. Sengwa et al. / Journal of Molecular Liquids 154 (2010) 117–123 of nearly equal viscosity components concluded that the maximum deviation in excess dielectric constant and viscosity properties occurs at same molar ratio, which is corresponding to the stoichiometric ratio of a stable adduct [1–4,9,13,25–27], but so far this fact is not examined for the mixed solvents of large viscosity difference constituents. 2. Experimental 2.1. Materials Grade reagents glycerol (Gly), N,N-dimethylformamide (DMF) and N,N-dimethylacetamide (DMA) were purchased from Himedia Laboratories and Loba Chemie of India. Binary mixtures of Gly with DMF and DMA were prepared at eleven volume concentrations over the entire mixing range at room temperature and simultaneously by weight measurements, the mole fractions of the mixture constituents were determined. 2.2. Measurements Values of the static dielectric constant ε0 of Gly, DMF and DMA and ε0m of the Gly–DMF and Gly–DMA binary mixtures were determined by using ‘capacitive measurement method’ at 1 MHz. Agilent 4284A precision LCR meter and a four terminal cell Agilent 16452A Liquid Dielectric Test Fixture were used for the measurement of capacitance of the cell without and with sample. The viscosity of the binary mixtures was measured using Fungilab alpha series rotational viscometer with a small sample holder. Viscosity of lower viscosity samples was made using Ostwald viscometer. The evaluated values of ε0m and η at Gly mole fractions, XGly of the Gly–DMF and Gly–DMA mixtures at different temperatures are tabulated in Table 1, and also plotted in Figs. 1 and 2, respectively. The measurement accuracy of the static dielectric constant values is ±0.3%, which is estimated by the calibration of the cell with the standard liquids by using their literature values of dielectric constant. All measurements were made at temperatures 285.15, 303.15, 318.15 and 333.15 K and the Table 1 Values of static dielectric constant ε0m and viscosity η (mPa s) of Gly–DMF and Gly– DMA binary mixtures at different temperatures, and activation energy ∆H⁎η (kJ/mol) at various mole fractions of Gly, XGly. XGly ε0m η 288.15 K ε0m η ε0m η ε0m η ∆H⁎η 303.15 K 318.15 K 333.15 K Gly–DMF binary mixtures 0.000 39.14 0.92 0.105 41.19 1.83 0.209 43.18 3.02 0.312 44.70 5.83 0.414 45.89 12.5 0.514 46.51 28.4 0.613 46.72 42.2 0.712 46.61 173.0 0.809 45.88 390.3 0.905 45.51 903.7 1.000 44.38 1966.7 36.55 39.08 41.14 42.25 43.39 43.74 43.81 43.80 43.34 42.69 41.17 0.77 1.50 2.41 4.22 7.36 14.2 19.9 64.6 127.5 258.7 520.6 34.73 36.75 38.75 39.56 40.42 40.91 41.03 40.87 40.55 39.69 38.99 0.64 1.24 1.84 2.91 4.77 8.35 10.7 27.3 50.5 91.1 182.5 32.98 34.05 36.20 36.86 37.87 38.15 38.41 38.30 37.80 37.07 36.48 0.56 1.01 1.49 2.23 3.51 5.48 6.79 14.5 23.7 40.5 72.8 8.9 10.5 12.7 17.3 22.6 29.2 32.5 44.2 49.7 55.2 58.3 Gly–DMA binary mixtures 0.000 40.59 1.07 0.124 41.60 2.78 0.241 42.77 5.00 0.353 43.85 10.5 0.459 44.40 25.2 0.560 44.83 62.9 0.656 45.12 151.7 0.748 45.24 316.4 0.836 45.25 648.1 0.920 44.72 1131.9 1.000 44.38 1966.7 37.72 38.92 39.92 41.01 41.57 41.96 42.05 42.15 42.11 41.62 41.17 0.86 2.21 3.92 7.04 12.8 29.9 61.6 120.7 204.4 335.7 520.6 35.39 36.46 37.46 38.56 39.15 39.59 39.74 39.8 39.86 39.27 38.99 0.71 1.78 3.01 4.79 7.81 17.6 26.3 43.2 75.9 117.4 182.5 32.68 33.94 35.04 36.08 36.81 37.12 37.32 37.34 37.21 36.73 36.48 0.62 1.48 2.31 3.62 5.39 9.41 13.9 20.4 33.3 48.9 72.8 9.7 11.2 13.7 19.1 27.3 33.1 42.7 49.2 52.7 55.8 58.3 Fig. 1. Plots of ε0m against mole fraction of Gly, XGly for (a) Gly–DMF and (b) Gly–DMA binary mixtures at temperatures 288.15 K (□); 303.15 K (○); 318.15 K (Δ) and 333.18 K (∇). In a and b, lines are smooth joining through the data points. temperature was controlled thermostatically within ±0.01 K using Thermo-Haake DC10 controller. 3. Data analysis The excess static dielectric constant εE for the binary mixtures is evaluated by the mole-fraction mixture law E ε = ε0m −ðε01 X1 + ε02 X2 Þ ð1Þ where X is the mole fraction and subscripts m, 1 and 2 represent the binary mixture and components 1 and 2 of the binary mixture, respectively. The evaluated εE values of the Gly–DMF and Gly–DMA binary mixtures were plotted against XGly in Fig. 3. The excess viscosity ηE for the binary mixture is evaluated by the mole-fraction mixture equation E η = η−ðη1 X1 + η2 X2 Þ ð2Þ where η is the experimental value of the viscosity of the binary mixture, X is the mole fraction and subscripts 1 and 2 represent the components 1 and 2 of the binary mixture, respectively. The evaluated ηE values of the Gly–DMF and Gly–DMA binary mixtures were plotted against, XGly in Fig. 4. 4. Results and discussion The thermodynamical parameters of an ideal liquid mixture of non-interacting dipolar molecules obey the linear behaviour with the R.J. Sengwa et al. / Journal of Molecular Liquids 154 (2010) 117–123 119 Fig. 2. Plots of η against mole fraction of Gly, XGly for (a) Gly–DMF and (b) Gly–DMA binary mixtures at temperatures 288.15 K (□); 303.15 K (○); 318.15 K (Δ) and 333.18 K (∇). In a and b, lines are smooth joining through the data points. Fig. 3. Plots of εE against mole fraction of Gly, XGly for (a) Gly–DMF and (b) Gly–DMA binary mixtures at temperatures 288.15 K (□); 303.15 K (○); 318.15 K (Δ) and 333.18 K (∇). In a and b, lines are non-linear fits. concentration of the mixture constituents. Figs. 1 and 2 show that the concentration dependent ε0m and log η values of Gly–DMF and Gly– DMA mixtures have significant deviation from ideal behaviour at all the investigated temperatures. The non-linear behaviour of these parameters confirms the H-bond complex formation over the entire mixing concentration range in the glycerol–amide mixtures. Figs. 1 and 2 indicate that the ε0m values are higher, whereas η values are lower than the ideal mixing behaviour. The measured ε0m values reflect the collective molecular contribution to the dielectric polarization at a given number of dipolar molecules per unit volume in a binary mixture. The enhancement in ε0m values reveals that the dipolar interaction between glycerol and amide molecules increases the net dielectric polarization of the mixture. But the decreases of η values confirm that the aggregated molecules mobility for viscous flow process increases in these binary mixtures. The excess dielectric constant εE and excess viscosity ηE values of the binary mixtures of polar solvents are frequently used to confirm the strength of hetero-molecular H-bonded structures and the stoichiometric composition corresponding to the formation of a stable complex adduct [1–30]. Fig. 3 shows the XGly concentration dependent εE values of the Gly–DMF and Gly–DMA binary mixtures. The moderate εE values at different temperatures may be due to nearly equal ε0 values of pure Gly and DMF/DMA. The large magnitude of ηE of the glycerol–amide mixtures (Fig. 4) is mainly due to a large difference in the viscosities of pure Gly and DMF/DMA. It is found that at all the investigated temperatures, the εE values of both the Gly– DMF and Gly–DMA mixtures have maximum deviation around XGly ∼ 0.5, whereas ηE values of Gly–DMF mixture and Gly–DMA mixture show the maximum deviation in the range XGly ∼ 0.73–0.75 and XGly ∼ 0.67–0.69, respectively (Table 2). These XGly concentrations are corresponding to the molar ratio of a stable complex adduct in the binary mixtures, which reveals that the molecular dielectric polarization process and the viscous flow process have different dominant complex species. 4.1. Stable complex adduct in dielectric polarization process In liquid mixtures of polar solvents, there is a formation of a variety of weak and strong H-bonded dipolar complex species of varying molar ratio and density (number of complexes in a unit volume), which are influenced by the concentration of the mixture constituents [15,31–36]. Some complex species are comparatively stable and contributes largely in the molecular polarization process of the binary mixtures. The density of such stable complex species also plays a governing role in the stabilization of the dielectric constant of the dipolar liquid mixture. The molar concentration XGly ∼ 0.5 corresponding to maximum εE values (Table 2) suggest the stable complex species of molar ratio 1:1 of Gly to DMF/DMA, which governs the molecular dipolar polarization of these binary mixtures. Further, it is observed that the maximum magnitude of εE values is almost temperature independent, which inferred that the density of 1:1 stable complex dipolar species remain same over the investigated temperature range. The positive εE values inferred that the H-bond hetero-molecular interaction between Gly and DMF/DMA increases the effective number of parallel aligned dipoles in the mixtures. Dielectric relaxation and Kirkwood correlation studies established that Gly is one of the most structured glass forming liquid because the molecular multimerization form the strong H-bonded three-dimensional molecular network [34–36]. The ends hydroxyl groups (primary alcohols groups) of Gly molecules contributed in the 120 R.J. Sengwa et al. / Journal of Molecular Liquids 154 (2010) 117–123 εEmax of Gly–DMF mixtures are nearly two times higher than that of Gly–DMA mixtures (Table 2), suggesting that either DMF form comparatively strong H-bond dipolar interactions with Gly molecules or the density of 1:1 complexes of Gly–DMF are higher than that of Gly–DMA. This behaviour may be due to the difference in molecular volume of DMF and DMA. The volume ratio of DMF to DMA is 0.83 [38]. We assume that the DMF and DMA molecules built-in via Hbonding into the 3D-structures of glycerol molecules, but due to comparatively smaller molecular size of DMF there is a higher probability of the large number of DMF molecules to built-in into Gly structures, resulting in the enhancement in Gly–DMF complex density as compared to that of Gly–DMA complexes and hence the εE values of Gly–DMF mixtures are found higher than that of Gly–DMA mixtures. Further, the presence of third methyl group in DMA molecules make them more polar than DMF as evidenced from slightly higher ε0 value of DMF. This results in the DMA selfassociation [38] and hinders the number of DMA molecules built-in into Gly structures and hence it seems that the Gly–DMA mixture have less number of 1:1 complexes as compared to that of Gly–DMF complexes. 4.2. Stable complex adduct in viscous flow process Fig. 4. Plots of ηE against mole fraction of Gly, XGly for (a) Gly–DMF and (b) Gly–DMA binary mixtures at temperatures 288.15 K (□); 303.15 K (○); 318.15 K (Δ) and 333.18 K (∇). In a and b, lines are non-linear fits. formation of strong H-bonded two-dimensional (2D) structure, which results in three-dimensional (3D) structure when secondary alcohol groups of Gly molecules form the cross-linkage H-bonding [34]. The DMF molecules in pure liquid state have no self-association, whereas DMA molecules in their pure liquid state form some H-bonded linear chain structures [18–24,31,37,38]. The positive εE values of Gly–DMF and Gly–DMA mixtures inferred that the interactions of DMF/DMA molecules with Gly act as structure breaker for some of the H-bonded cross-linked Gly dipoles and simultaneously oriented them in planar structure with parallel alignment, which results the enhancement in net dielectric polarization. The symmetrical shape of concentration dependent εE values of Gly–DMF and Gly–DMA mixtures (Fig. 3) indicates that the dominant mode of 1:1 complex species is unaffected by addition of a small amount of DMA into Gly or vice-versa. The maximum values of εE i.e., Table 2 Values of XGly corresponding to maximum magnitude of excess dielectric constant εEmax and viscosity ηEmax (mPa s) of Gly–amides binary mixtures at different temperatures. Temperature (K) XGly εE(max) XGly −ηE(max) Gly–DMF binary mixture 288.15 303.15 318.15 333.15 0.50 0.47 0.48 0.50 4.44 4.79 4.03 3.77 0.75 0.73 0.74 0.73 1247.03 318.08 120.89 44.39 Gly–DMA binary mixture 288.15 303.15 318.15 333.15 0.54 0.55 0.55 0.52 2.18 2.32 2.20 2.38 0.68 0.67 0.68 0.69 1156.31 282.18 95.67 34.15 The molar concentration corresponding to maximum magnitude of excess viscosity ηEmax for glycerol–amide mixtures (Table 2) suggest the complex entities probably 3Gly:DMF and 2Gly:DMA being the unique flow species for a cooperative hetero-molecular viscous process. The negative ηE values suggest that the flow process is facilitated by the hetero-molecular interactions in these systems. A large change in the magnitude of negative ηE values with the temperature variation inferred that the number of the viscous flow complex species significantly influences by the temperature. This is probably due to intermolecular vibrations and thermal motion that may weaken the hydrogen bond connectivity of these complex species and facilitates their translational and rotational molecular motion in viscous flow. The asymmetrical shape of the concentration dependent ηE (Fig. 4) curves indicate that the addition of a small amount of DMF/DMA to Gly involves a more important effect on the breaking of Gly structures and simultaneously formation of a large number of 3Gly:DMF and 2Gly:DMA complex species, which favours the viscous flow process. Similar shape of the concentration dependent ηE values was also observed for the binary mixtures of glycerol with monohydric alcohols [39]. Comparative excess dielectric constant and viscosity results evidence that in viscous flow the translational molecular motion governs their stable complex entity and masked the contribution of rotational dipolar complex adduct. Further, it is found that the magnitude of negative ηE values of Gly–DMF is higher than that of Gly–DMA, which suggests that the volume effect of DMF and DMA molecules also influences the number of dominant complex species in viscous flow process. 4.3. Arrhenius behaviour The log η values of Gly–DMF and Gly–DMA mixtures are plotted against reciprocal of the absolute temperature (1/T) in Fig. 5, which demonstrates the Arrhenius type behaviour (i.e., log η are the linear function of 1/T) at all the compositions of the mixed solvents. The apparent activation energy or a heat of activation ∆Hη⁎ for a viscous flow is represented by the Arrhenius relation for rate coefficients [40] h i  η = A exp ΔΗη = RT ð3Þ where A is pre-exponential factor which is independent of temperature T and R is a gas constant. The values of ∆Hη⁎ were determined R.J. Sengwa et al. / Journal of Molecular Liquids 154 (2010) 117–123 121 The evaluated ∆Hη⁎ values for glycerol–amides are plotted against, XGly in Fig. 6 and also recorded in Table 1. The evaluated ∆Hη⁎ of pure glycerol is found in good agreement with the literature value [39–41]. It is observed that the ∆Hη⁎ values of Gly–DMF and Gly–DMA increases non-linearly with increase of XGly concentration (Fig. 6) and shows a significant difference for these mixtures around the molar ratio of a stable adduct for viscous flow. Further, ∆Hη⁎ values of Gly–DMA were found higher than that of the Gly–DMF mixtures over the XGly range from ∼0.4 to 0.85, which is attributed to the molecular volume effect of DMF and DMA. Fig. 7, shows the Arrhenius behaviour of the maximum values of ηE i.e., ηEmax of the glycerol–amide binary mixtures. It is found that for these binary mixtures ηEmax plots against 1/T obey the straight line behaviour. The temperature dependence of dielectric constant ε0m(T) and its derivative (∂ε0m/∂T) reflects a behaviour of the electric-field-induced increment of the basic thermodynamic quantities ΔU, ΔS, ΔF of the sample at a given number of dipole molecules per unit volume [42–44]. For the dielectric material under the applied field strength E, the increments of the internal energy ΔU, the entropy ΔS, and the Helmholtz free energy ΔF are given by the equations [42–44] Fig. 5. Arrhenius plots of log η against reciprocal of temperature for (a) Gly–DMF binary mixtures at mole fractions of Gly, XGly = 0.000 (□); 0.105 (○); 0.209 (Δ); 0.311 (∇); 0.414 (◊); 0.514 (■); 0.613 (●); 0.712 (▲); 0.809 (▼); 0.905 (♦); and 1.000 ( ) and (b) Gly–DMA binary mixtures at mole fractions of Gly, XGly = 0.000 (□); 0.124 (○); 0.241 (Δ); 0.353 (∇); 0.459 (◊); 0.560 (■); 0.656 (●); 0.748 (▲); 0.836 (▼); 0.920 (♦); and 1.000 ( ). The lines are linear fits of the data points. from the slope of Arrhenius plots (log η against 1/T) of the glycerol– amide mixtures (Fig. 5) by the relation [40]  ΔHη = 2:303 R ½d logη = dð1 = T ފ ð4Þ Fig. 6. Plot of ∆H⁎η against mole fraction of Gly, XGly for Gly–DMF (□) and Gly–DMA (○) binary mixtures. Lines are non-linear fits of the data points.   ΔU U ðT; EÞ−U0 ðT Þ ε ∂ε ≅ = 0 ε0m + T 0m 2 2 2 ∂T E E ð5Þ   ΔS SðT; EÞ−S0 ðT Þ ε ∂ε0m ≅ = 0 2 2 2 ∂T E E ð6Þ ΔF F ðT; EÞ−F0 ðT Þ ε ≅ = 0 ε0m 2 E2 E2 ð7Þ where U0, S0 and F0 denote the values of the thermodynamic quantities in the absence of electric field E, T is the absolute temperature and ε0 = 8.85 pF/m is the permittivity of free space or vacuum. In Eq. (5), the term 0.5ε0T ∂ε0m/∂T is a measure of the dielectric internal energy, which is converted into heat during the isothermal charging of the capacitor filled with a dielectric material (binary mixture) of the static dielectric constant ε0m, whereas 0.5ε0ε0m represent the dielectric energy stored in the capacitor. Therefore the difference ΔF = F(T,E) − F0(T) is a maximum of the energy, which can be yielded during the isothermal discharge of the capacitor filled with the dielectric material [43,44], which is that of the static permittivity itself as illustrated in Fig. 8 for the glycerol–amide mixtures. The ΔF per unit volume and unit field strength exhibits a decrease with increase of temperature for the studied glycerol–amide mixtures (Fig. 8). Fig. 9 illustrate the ΔS = S(T,E) − S0(T) which is directly Fig. 7. Plots of −ηEmax against reciprocal of temperature for Gly–DMF (□) and Gly–DMA (○) binary mixtures. The lines are linear fits of the data points. 122 R.J. Sengwa et al. / Journal of Molecular Liquids 154 (2010) 117–123 related with the sign of the temperature derivative of the dielectric constant. The negative values of ΔS (per unit volume and per unit field strength per kelvin) (Fig. 9) confirm that, under the influence of electric field, the entropy of glycerol–amide mixtures decreases, that confirms the increase in molecular order of the system, which is normal behaviour of the dipolar liquids [40]. Further, Fig. 9 shows that a large change in the entropy values for Gly–DMF mixtures with the concentration variation of XGly, whereas in Gly–DMA binary mixtures the entropy values are almost independent of the mixture constituent concentration. 5. Conclusions Fig. 8. Temperature dependent plots of static dielectric constant ε0m and the Helmholtz free energy ΔF/E2 for (a) Gly–DMF binary mixtures at mole fractions of Gly, XGly 0.000 (□); 0.105 (○); 0.209 (Δ); 0.311 (∇); 0.414 (◊); 0.514 (■); 0.613 (●); 0.712 (▲); 0.809 (▼); 0.905 (♦); and 1.000 ( ) and (b) Gly–DMA binary mixtures at mole fractions of Gly, XGly 0.000 (□); 0.124 (○); 0.241 (Δ); 0.353 (∇); 0.459 (◊); 0.560 (■); 0.656 (●); 0.748 (▲); 0.836 (▼); 0.920 (♦); and 1.000 ( ). The lines are linear fits of the data points. The static dielectric constant and viscosity of the Gly–DMF and Gly–DMA binary mixtures at 288.15, 303.15, 318.15 and 333.15 K, have been measured over the whole composition range. The nonlinear behaviour of these parameters with one of the contituent concentration confirms the formation of hetero-molecular H-bond interaction in the binary system. The 1:1 complex species of Gly to DMF/DMA governs the dielectric polarization process and their behaviour is almost temperature independent. The comparative magnitude of excess dielectric constant values inferred that the density of 1:1 complex species in Gly–DMF mixtures are twice that of Gly–DMA mixtures, which is governed by their molecular volume effect. The 3Gly:DMF and the 2Gly:DMA complex species govern the viscous flow process of Gly–DMF and Gly–DMA binary mixtures, respectively, and their density is significantly influenced by the temperature variation. Results suggest that the Gly–DMF and Gly– DMA mixed solvents have moderate H-bond interaction strength of the complex species which contributed in molecular polarization process. The dielectric constant and viscosity behaviour of glycerol– amide mixtures obey the Arrhenius type behaviour over the investigated temperature range. 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