RHEOLOGICAL INVESTIGATION OF FORM RELAXATION AND INTERFACE RELAXATIONPROCESSES IN POLYMER BLENDS

Transmission electron microscopical and theological investigations hav e 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 correspondin g diblock copolymer, and C-b-B is a diblock copolymer with poly(cycloh exyl methacrylate) (C) being thermodynamically miscible with A. The sp here-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 blend s compared with the A/A-b-B/B blends prove the efficiency of the entha lpic acting compatibilizer. The theological material functions G' and G '' were used to calculate relaxation time spectra and to determine c haracteristic relaxation times. The form relaxation time tau(1) for th e relaxation of the ellipsoidally deformed soft PS-particles back to s pheres have been verified for all blends no matter whether they where compatibilized or not. An additional relaxation time tau(beta) was fou nd for both types of compatibilized blends. This time is assigned to a non-isotropic interfacial stress, which may arise from relaxation pro cesses of the block copolymers at the interface.