Determination of mutual diffusion coefficients at nonsymmetric polymer/polymer interfaces from rheometry

A novel method for determining the mutual diffusion coefficient using rheom etry is presented. The method includes mathematical modeling for mutual dif fusion at polymer/polymer interfaces and experimental determination of mate rial parameters for the model. The model combines the concepts of the repta tion theory and the fast-mode model applied to miscible dissimilar polymers brought into intimate contact in the molten state. The material parameters for the model are obtained from experiments in which the dynamic complex s hear modulus, G*, is measured in parallel-plate geometry under small amplit ude of deformation as a function of time and frequency for a sandwich-like assembly. The technique was applied to the poly(methyl methacrylate) (PMMA) /poly(styrene acrylonitrile) (SAN) system, and the measured mutual diffusio n coefficient was found to be in agreement with the values reported in the literature for the same system.