Determination of Mutual Diffusion Coefficients at Nonsymmetric Polymer/Polymer Interfaces from Rheometry

A novel method for determining the mutual diffusion coefficient using rheometry is presented. The method includes mathematical modeling for mutual diffusion at polymer/polymer interfaces and experimental determination of material parameters for the model. The model combines the concepts of the reptation 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 shear modulus, G *, is measured in parallel-plate geometry under small amplitude 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 diffusion coefficient was found to be in agreement with the values reported in the literature for the same system.