STATIC AND DYNAMIC LIGHT-SCATTERING FROM POLYSTYRENE POLY(DIMETHYLSILOXANE)/POLY(METHYL METHACRYLATE)/TOLUENE SOLUTIONS/

The static and dynamic scattering properties of polystyrene (PS)/poly( dimethylsiloxane) (PDMS)/poly(methyl methacrylate) (PMMA)/toluene solu tions are investigated in the conditions of homogeneous single-phase m ixtures. The cases of PS/PDMS/toluene and PS/PMMA/toluene were investi gated previously in our laboratory, and the purpose of this work is to see the effects of a third polymer in the mixture. The parameters are chosen in such a way that the so-called optical theta condition is fu lfilled for the visible components, and the scattered light probes dir ectly the composition fluctuations of the PS/PDMS blend in a matrix of toluene + PMMA. The data show that the presence of PMMA does not chan ge dramatically the qualitative behavior of the scattering properties and affects essentially their values. The results which are obtained i ndependently from static and dynamic measurements are self-consistent. The quasi-elastic data suggest that the hydrodynamic interaction is s creened out in the range of concentrations considered in this work. Th e theoretical framework used to analyze the data is based on the rando m-phase approximation and is found to be sufficient within the conditi ons of our experiments as long as the mixtures remain stable in a stat e of a single homogeneous phase.