Particle Scattering Factor and Segment–Segment Distance Distribution of Macromolecules in Solution

Abstract

The angular dependence of light scattering from solutions of three samples of poly‐α‐methylstyrene in various solvents has been measured over a wide range of scattering angles. For molecules with a radius of gyration larger than about 500 Å, differences (δP) are found between the actual angular dependence (P) and the one (P id ) predicted—with Debye's equation—for ideal Gaussian coils. By subjecting the measured data to a statistical analysis, a quantitative description of δP was attained. The quantities δP contain information about the function δW(r) , which is the difference between W(r) and W id (r) ; the function W(r) is the actual distribution function for the distances between the segments in a polymer coil, whereas W id (r) is the one that follows from random‐flight statistics, underlying the ideal Gaussian coil model. The information about δW(r) was obtained by applying a Fourier inversion to the measured δP curves. Although this information is necessarily limited, the typical features of δW(r) thus found correspond with those a realistic function W(r) must possess in order to account for the impossibility of chain intersections (excluded volume effect).