DYNAMIC LIGHT-SCATTERING EXPERIMENTS ON PVME POLYSTYRENE TOLUENE AND PVME POLYSTYRENE CARBON-TETRACHLORIDE SOLUTIONS

The results of dynamic light scattering experiments on poly(vinyl meth yl ether)-polystyrene-toluene and poly(vinyl methyl ether)-polystyrene -carbon tetrachloride solutions are presented. In each of these system s, the poly(vinyl methyl ether) (PVME) is approximately isorefractive with the solvent and the polystyrene (PS) is present only as a trace. The results of our experiments on PVME-PS-toluene solutions agree with previous work, giving the self-diffusion coefficient of the PS. Howev er, a change of solvent from toluene to carbon tetrachloride produces much lower values for the effective diffusion coefficients. It is conc luded that the true self-diffusion coefficient is no longer measured b y this technique due to the solvent being of good quality for one poly mer but only marginal for the other. This result is discussed in the c ontext of theoretical studies of dynamic scattering from ternary polym er solutions. The scattering vector dependence of the effective diffus ion coefficient obtained from cumulant fits to the DLS data is also st udied.