Rheological investigation of form relaxation and interface relaxation processes in polymer blends

Summary Transmission electron microscopical and rheological investigations have been performed on polymer blend systems of the type A/B, A/A-b-B/B, and A/C-b-B/B, where B is poly(methyl methacrylate) as the continuous and A is polystyrene as the dispersed phase. A-b-B is the corresponding diblock copolymer, and C-b-B is a diblock copolymer with poly(cyclohexyl methacrylate) (C) being thermodynamically miscible with A. The sphere-size distribution was estimated from the TEM data and found to be monomodal for all blends. Smaller sphere sizes in the A/C-b-B/B blends compared with the A/A-b-B/B blends prove the efficiency of the enthalpic acting compatibilizer.The rheological material functions G and G were used to calculate relaxation time spectra and to determine characteristic relaxation times. The form relaxation time ₁ for the relaxation of the ellipsoidally deformed soft PS-particles back to spheres have been verified for all blends no matter whether they where compatibilized or not. An additional relaxation time was found for both types of compatibilized blends. This time is assigned to a non-isotropic interfacial stress, which may arise from relaxation processes of the block copolymers at the interface.