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Title: Study of solvent effect on microwave dielectric relaxation and molecular dynamics in PVP-PEG mixtures
Authors: Sengwa, R J
Keywords: Dielectric relaxation;Molecular dynamics;Poly(vinyl pyrrolidone)
Issue Date: Feb-2004
Publisher: NISCAIR-CSIR, India
IPC Code: G01R 22/00
Abstract: The dielectric relaxation of poly(vinyl pyrrolidone) (PVP) (Mw=40000 g mol-1) and poly(ethylene glycol)s (PEG)(Mw = 200 and 400 g mol-1) and their binary mixtures in dilute solutions of dioxane has been studied performed at 10.1 GHz and 35°C. The average relaxation time τ o, relaxation time corresponding to segmental motion τ 1 and group rotations, τ 2, distribution parameter α and free energy of activation ΔF τ, of these mixtures has been determined. These results have been compared with the values of relaxation times obtained earlier in benzene solutions to explore the affect of solvent environment on molecular dynamics. The values of α for PVP-PEG200 and PVP-PEG400 were found in the range of ≈ 0.18 - 0.75. The anomalous variation in the values of τo and τ1 of these binary systems has been studied by considering the stretching effect in PEG molecular chain length in dilute solutions and the number of hydrogen bonding between carbonyl groups of PVP monomer units and terminal hydroxyl groups of PEGs in complex heterogeneous network. Further, in both benzene and dioxane solvents the τ2 values of PVP-PEGs mixtures are found to be nearly equal. This shows that group rotation is independent of the nature of solvation medium and attributed to the rotation of PEG chain ends -OH groups about the C-O bond in dynamic equilibrium. The relaxation times of PVP-PEGs in dilute solutions are found to be independent of the mixtures and solvent viscosity. The variations in dipole moment α values of PEGs molecules in different solvents were explored by incorporating the solute-solvent interactions in hydrogen-bonding non-polar solvents.
Page(s): 142-148
ISSN: 0975-1041 (Online); 0019-5596 (Print)
Appears in Collections:IJPAP Vol.42(02) [February 2004]

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