PHASE-SEPARATION AND GLASS-TRANSITION INTERVENTION IN A POLYMER BLEND

We report on a dynamic-light-scattering study of the order parameter f luctuations in a binary mixture of poly(methylphenylsiloxane) and poly (styrene) in the glass transition region. We find that the interdiffus ion freezes and the growth of composition fluctuations ceases when the time scales of the segmental motion in the poly(styrene)-rich environ ment approach the duration of the experiment. In contrast to the singl e relaxation process found in polymer blends well above T-g, the polym er mixture studied here exhibits an additional slower relaxation mode.