Variation of refractive index of polystyrene with molecular weight: Effect on the determination of molecular weight distributions

Abstract

Abstract Sensitive refractive index measurements on solutions have indicated that the narrow molecular weight polystyrene samples prepared by the Mellon Institute method exhibit a small systematic molecular weight–refractive index dependence up to 300,000 and higher. This upper limit is higher than had previously been suggested. Sensible consistency is generally assumed above a few thousand molecular weight. The effect on this molecular weight–refractive index dependence on gel permeation chromatography and light‐scattering molecular weight measurements on polystyrene standards is illustrated.