Thermal and Mass Diffusion in a Semidilute Good Solvent-Polymer Solution

Published

August 1, 1999

Author(s)

K J. Zhang, M E. Briggs, R W. Gammon, J V. Sengers, Jack F. Douglas

Abstract

The Soret coefficient S_T and collective (mass) diffusion coefficient D_c of polystyrene dissolved in the good solvent toluene is measured over a range of concentrations and molecular weights using an optical beam deflection method. Our measurements indicate that S_T scales inversely with the polymer translational diffusion coefficient in dilution solutions and exhibits a power law scaling with polymer concentration and an independence of polymer molecular weight in semi-dilute solutions. These findings are consistent with the known scaling of 1/D_c in dilute and semi-dilute polymer solutions, the relative insensitivity of the thermal diffusion coefficient D_Th of polystyrene in toluene to polymer concentration, and the relation S_T = D_Th/D_c from irreversible thermodynamics. We were able to represent our S_T and D_c data by theoretically motivated reduced concentration master curves, but the concentration-molecular weight scaling variable were found to be different for each transport property -- a result contrary to theoretical expectations. However, the asymptotic concentration scaling exponents deduced from these data fits are compatible with DeGennes' scaling arguments for D_c and with modern estimates at the chain size exponent Ņ for swollen polymers in a good solvent.

Citation

Journal of Chemical Physics

Volume

111

Issue

No. 5

Pub Type

Journals

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Keywords

collective diffusion coefficient, polymer solutions, Soret coefficient, temperature gradient, thermal diffusion coefficient

Citation

Zhang, K. , Briggs, M. , Gammon, R. , Sengers, J. and Douglas, J. (1999), Thermal and Mass Diffusion in a Semidilute Good Solvent-Polymer Solution, Journal of Chemical Physics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851552 (Accessed September 8, 2024)