Osmotic pressure of polystyrene in toluene solutions, measured over wide ranges of concentration and degree of polymerization of the polymer

Abstract

The osmotic pressure in solutions of polystyrene in toluene is measured as a function of concentration and degree of plymerization of the polymer. The volume fraction of the polymer in the solution studied ranges up to 0.15, and the degree of polymerization of the practically monodisperse polymers ranges from 40 to 6000. The experimental data are discussed in terms of the parameter q, defined as the ratio between the number of nearest neighbours of a polymer molecule, and the number of nearest neighbours of a solvent molecule. All estimated values of q are smaller than 0.25 r, where r is the degree of polymerization of the polymers. This result is taken as experimental evidence that in solutions of polystyrene in toluene less than one fourth of the surface area of a polymer segment is exposed to the solvent. The maximal value of q/r is observed for the most concentrated solutions studied, and for dilute solutions of polystyrene with a degree of polymerization below 100.