Calculation and experimental verification of concentration profiles for selected species at the interphase generated by diffusion in polymer pairs

A method for calculating diffusion rates for individual species in concentrated regime is outlined. The effects of monomeric friction coefficient, Flory–Huggins thermodynamic interaction parameter, individual species molecular weights, local molecular weights distribution, and local T_g are precisely calculated. The method is used to calculate individual concentration profiles generated by diffusion of multicomponent polymer blends, and experimentally tested. Polystyrene with a bimodal molecular weight distribution is allowed to diffuse in a blend of polyphenylene oxide and polystyrene. Local physical properties change markedly along the interdiffusion path and, therefore, this is a demanding test for the proposed calculation method. The simulated concentration profiles are compared with results obtained by using two independent experimental techniques: Raman spectroscopy and dynamic mechanical analyzer (DMA). The total polystyrene (PS) concentration profiles, calculated using the proposed method, agree well with Raman spectroscopy results. Simulated DMA results—which are sensitive to the PS species molecular weight distribution—obtained using the concentration profiles, calculated for each PS molecular weight species agree well with the experimental DMA results. Calculations based on average molecular weights give incorrect results. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 3097–3107, 1999