The Frictional Coefficient for Flexible Chain Molecules in Dilute Solution

Abstract

The frictional coefficient, f0, of a polymer molecule in dilute solution is assumed to vary directly as an average linear dimension of the chain. From this assumption equations are developed, as follows, which are analogous to those used successfully in the interpretation of intrinsic viscosity measurements; f0/η0 =KfM½α and Kf=P(〈r02〉/M)½ where α represents the factor by which the actual root-mean-square end-to-end distance exceeds the unperturbed distance (〈r02〉)½, M is the molecular weight, η0 the viscosity of the medium, and P should be a universal constant. Data in the literature on the dependence on molecular weight of sedimentation constants and diffusion coefficients, extrapolated to infinite dilution confirm the conclusions drawn from these equations.