MICROMECHANICAL AND MICRODIELECTRIC TRANSITIONS IN P(S-G-EO) MODIFIEDPPO PMMA BLENDS/

The effect of two poly(styrene-graft-ethylene oxide)s with different g raft lengths and graft densities on the interphase properties of poly( 2,6-dimethyl-1,4-phenylene oxide)/poly(methyl methacrylate) (PPO/PMMA) blends was studied by different techniques. The miscibility between t he copolymers and the homopolymers, as well as the phase reduction in the ternary blends, was favoured by longer and more separated grafts. Transmission electron microscopy shows that the addition of any of the copolymers leads to the formation of an interphase between the hetero geneous PPO and PMMA phases. The ternary blends present micromechanica l and microdielectric transitions at temperatures in the range 60-100 degrees C, where the transition temperatures decrease with increasing copolymer contents. The micromechanical and microdielectric transition s originate from the change in the relative moduli values and the diel ectric losses of the matrix, interphase and particle phase of the tern ary blends. (C) 1997 Elsevier Science Ltd.