EVOLUTION OF PHASE MORPHOLOGY IN COMPATIBILIZED POLYMER BLENDS AT CONSTANT QUENCH DEPTHS - COMPLEMENTARY STUDIES BY LIGHT-SCATTERING AND TRANSMISSION ELECTRON-MICROSCOPY

The effect of added block copolymer on the phase separation and morpho logy evolution in a partially miscible blend of polystyrene and polybu tadiene near the critical composition is studied by temperature jump l ight scattering (TJLS) and transmission electron microscopy (TEM). As block copolymer is added, the phase boundary is shifted to lower tempe ratures and the phase separation process is slowed dramatically. Since the quench depth greatly affects the rate of phase separation in any blend system, we have used equivalent quench depths by adjusting for t he shift in the phase boundary as block copolymer is added. The morpho logy evolution of these ternary blends was studied by preparing TEM sp ecimens at equivalent shallow quench depths (Delta T = 1.6 degrees C) and allowing each blend mixture to coarsen for the time required to re ach a specific constant size, or q-value, using the TJLS data on the k inetics of phase separation. The q-range selected was q similar to 0.0 03-0.005 nm(-1), which corresponds to a spacing of 1-2 mu m in real sp ace. The combination of light scattering and microscopy techniques mor e rigorously describes the compatibilization process in these complex ternary systems.