MOLECULAR RELAXATION IN THE BLENDS OF POLYSTYRENE POLY(2,6-DIMETHYL-1,4-PHENYLENE OXIDE) AT LOW-TEMPERATURE/

Molecular relaxation behavior in terms of the alpha, beta, and gamma t ransitions of miscible PS/PPO blends has been studied by means of DMTA and preliminary work has been carried out using DSC. From DSC and DMT A (by tan delta), the observed cr relaxation (T-alpha or T-g) of PS, P PO, and the blends, which are intermediate between the constituents, a re in good agreement with earlier reports by others. In addition, the beta transition (T-beta) of PS at 0.03 Hz and 1 Hz is observed at -30 and 20 degrees C, respectively, while the gamma relaxation (T-gamma) i s not observed at either frequency. The T-beta of PPO is 30 degrees C at 0.03 Hz and is not observed at 1 Hz, while the T-gamma is -85 degre es 0 at 0.03 Hz and -70 degrees C at 1 Hz. On the other hand, blend co mposition-independent beta or gamma relaxation observed in the blends may be a consequence of the absence of intra- or intermolecular intera ction between the constituents at low temperature. Thus it is suggeste d that at low temperature, the beta relaxation of PS be influenced sol ely by the local motion of the phenylene ring, and that the beta or ga mma relaxation of PPO be predominated by the local cooperative motions of several monomer units or the rotational motion of the methyl group in PPO. (C) 1998 John Wiley & Sons, Inc.