Fractional coefficient of macromolecules in concentrated solution and in the vicinity of the critical solution temperature. Diffusion and sedimentation studies of polystyrene in toluene and trans-decalin

The concentration dependence of the frictional coefficient (f) in concentrated solutions of well-defined polystyrene fractions has been studied both in a good solvent (toluene) and in a solvent where θ conditions and condition in the vicinity of phase separation can be realized (trans-decalin). f and the self-diffusion coefficient (D⁺) have been calculated from a combination of measured translational diffusion coefficients (D) and osmotic pressure data for the systems; polystyrene $\text{(M = 390 000)}\text{trans-}\text{decalin}$ up to 90 kg/m³ at 20° (θ-conditions), 30° and 40°C; polystyrene $\text{(M = 110 000)}\text{toluene}$ up to 120 kg/m³ at 25°C. Sedimentation measurements are also reported. The main results are: (a) over a concentration interval 0–100 kg/m³, f shows more than a ten-fold and almost linear increase; (b) in trans-decalin when the temperature is raised from 20° (θ-conditions) to 40°C (good solvent conditions), keeping the concentration constant, f increases only slightly, the increase being somewhat more pronounced at higher concentrations; (c) the concentration dependence of the ratio $\text{D}\text{D}{}^{\mathrm{+}}$ is considerable under good solvent conditions but becomes gradually less pronounced when θ-conditions are approached; (d) diffusion/osmosis and velocity sedimentation give identical values of f over the entire concentration interval.