ORIENTATION AND RELAXATION IN UNIAXIALLY STRETCHED STYRENE-CO-METHYL METHACRYLATE RANDOM COPOLYMERS

Orientation and relaxation behavior in uniaxially stretched styrene-co -methyl methacrylate random copolymers was investigated. When compared at a reference temperature T = T-g + constant, orientation of methyl methacrylate units (MMA) decreases while styrene units orientation inc reases with a decrease in the styrene percentage. This behavior can be related to intermolecular interactions between MMA units and to the s tiffness of styrene-MMA units, which do not undergo conformational cha nges upon stretching. Both monomer units relax the same in a given cop olymer and chain relaxation increases when the styrene percentage incr eases. Orientation relaxation of styrene and MMA units can be reduced to two general relaxation master curves whatever the blend composition , when the results are compared at same monomeric friction coefficient . (C) 1994 John Wiley and Sons, Inc.