Light Scattering Investigation of the Structure of Polystyrene

Abstract

Using light scattering, the mean square molecular radius and length of a number of samples of polystyrene have been measured as a function of solvent and temperature. Molecular weights, intrinsic viscosities, and ``osmotic second virial coefficients'' have also been determined on many of the samples. From the data it may be concluded: (1) that polystyrene molecules are extended and stiffened by steric interactions of the phenyl groups; (2) that the molecules are largely unbranched; (3) that the heat of dilution is negative in some solvents, contrary to the usual situation in hydrocarbon systems; (4) that the osmotic second virial coefficient depends strikingly on molecular weight for a given solvent; (5) that there is a good correlation between this coefficient and the mean square radius at a given molecular weight; (6) that the intrinsic viscosity is strictly proportional to a power of the molecular weight over the molecular weight range from 2,000 to 2,000,000, but that deviations occur at lower molecular weights; (7) that the intrinsic viscosity and mean square radius are functions of solvent at high molecular weights but not at very low molecular weights. Theoretical concepts necessitated by these observations are discussed briefly.