Etude par pression osmotique de polystyrenes lineaires et ramifies en solution: determination de leurs parametres thermodynamiques

Osmotic pressure measurements have been carried out with moderately concentrated solutions (v₂ ? 0·1 g/cm³) of linear and branched polystyrenes in good and poor solvents at various temperatures. The experimental study of star- and comb-shaped polystyrenes with high segment density leads to the following conclusions: (1) we confirm the lowering of the Flory “theta” temperature of these polymers with respect to that of linear homologues, already found by light scattering technique. (2) We show that, in the low concentration range, the polymer solvent interaction parameter % depends not only upon the polymer concentration but also is a function of the intramolecular volume fraction within the polymer coil: this effect tends to disappear at high concentrations.