Light Scattering from Mixtures of Two Polystyrenes in Toluene and Self-Diffusion Coefficients

Abstract

Experimental light scattering data from solutions consisting of two nearly monodisperse different molecular weight polystyrenes in toluene are interpreted using a theoretical approach recently developed in our laboratory. By allowing polystyrene chains with different chain lengths to have different monomer friction coefficients and different excluded volume parameters, we have provided an excellent theoretical model for this ternary polymer solution over a wide concentration range. The self-diffusion coefficients of two polystyrenes in various concentrations are calculated from diffusivity matrix elements. The results obtained are found to be consistent with those obtained by using different techniques.

Quasielastic Light Scattering Study of Self-Diffusion and Interaction of Two Homopolymers in an Arbitrary Solvent

“…In the above equation, if a 2 = 0 (solvent is index matched to polymer-2) is assumed, one reduces eq 17 to A - /( A - + A + ) = ( D + D - / D 22 − D + )/( D - − D + ), which was obtained previously. , On the other hand, if a 1 = a 2 (two polymers differ only in molecular weight), one obtains which was previously used in analyzing the ternary system consisting of PS-1/PS-2/toluene …”

“…From the theory, we have found useful expressions and have reduced and simplified Benmouna's result, thereby facilitating data analysis in polymer systems of practical interest. , In both ours and Benmouna's theory, the random phase approximation (RPA) , is used. The RPA gives a good interpretation of the QELS spectra of ternary polymer solutions over a wide concentration range . Also with the aid of the RPA, Desbrieres et al have proposed a method to determine the self-diffusion coefficients of two polymers and the Flory−Huggins interaction parameter of the constitute polymers in a ternary polymer solution by QELS .…”