Solvent Isotope Effect on Viscosity of Polystyrene-Benzene Solutions

The concentration and temperature dependences of viscosity and density of solutions of nearly monodisperse polystyrene samples (Mw/Mn < 1.06) in benzene and deuterated benzene have been determined. The measurements were conducted with samples of different molecular weights (Mw ) ranging from 4_103 to 4_105 between 293-313 K. Isotope H/D substitution in benzene causes visible changes in viscosity and density of solutions, however, its influence on intrinsic viscosities and Huggins constants, derived from the concentration dependences of viscosity, is negligible. No isotope effects on the exponents in the power law relationships have been detected. The viscosities of the solutions have been also correlated with the densities. The apparent close-packed volumes are practically constant for all solutions and seem to be determined by the properties of the solvent. The deuterium substitution visibly affects the close-packed volumes - they decrease by approximately 13%, both in pure solvent and in solutions.