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

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