DIELECTRIC-RELAXATION BEHAVIOR OF STYRENE BUTYL ACRYLATE COPOLYMERS NEAR T-G

The dielectric relaxation behavior of copolymers of styrene and butyl acrylate is investigated over a wide frequency range. The results are analyzed in terms of the free volume and configurational entropy theor ies. The calculated fractional free volume was nearly constant over th e composition range studied while the volume expansion coefficient exh ibits a maximum in the mid composition range. Even though the change i n heat capacity at T-g varied linearly with composition, the free ener gy of activation calculated from the configurational entropy model rea ched a broad maximum in the mid composition range. In addition, the av erage dielectric relaxation time of the copolymers at T-g is not const ant. In fact, the longest relaxation times were obtained for samples c ontaining nearly equal amounts of styrene (S) and butyl acrylate (B). It is suggested that the SB diad has a relaxation time much longer tha n the relaxation times of the SS and BB diads.