Incompatibility of polymer solutions. II. Concentration and angle dependence of the light scattering in the system polystyrene + polyisobutylene + toluene

Light scattering experiments are described on the system polystyrene (PS) + polyisobutylene (PIB) + toluene at constant temperature. At a fixed concentration of the nearly “invisible” PIB the light scattering at various angles was measured as a function of varying PS concentration up to the region of incompatibility. For interpretation of the results use is made of an extension of the classical fluctuation theory for multicomponent systems to finite scattering angles. The experimental data can be described qualitatively with this theory. Addition of a second polymer has little influence on the size of the other polymer. The variation of the light scattering with the wavelength can be explained in terms of the (negative) adsorption of one polymer by the other.