Dynamics and Morphology of Anisotropic Phase Separation of Polymar Blends Cross-linked by Unearly Polarized light.

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This research project has two purposes : inducing anisotropic phase separation polymer blends by taking advantages of polarization-selective reactions and establishing novel method for morphology control of polymer blends. The first purpose was attained by using linear polarized light to selectively induce chemical reactions between component of binary polymer blends. By doing so, the spatial symmetry of concentration fluctuations is broken, leading to anisotropic phase separation. In order to elucidate the consequence of this symmetry breaking process on the resulting morphology of the reacting blends, two typical reactions, i.e. cross-linking and non-cross-linking , were utilized in the experiments. To facilitate the experiments, mixtures of polystyrene (P5 and poly(vinyl methyl ether) (PVME) which have a well-known lower critical solution temperature (LCST), were used in this research project. Only the PS component was chemically modified for the purpose by labeling with either anth … More racene (PSA) or tram-stilbene (PSS). PS/P VME blends were destabilized by either the cross-linking reactor between PSA chains via photodimerization of anthracene or the photoisomerization of the stilbene moieties labeled on the PSS chains. The following results were obtained b irradiating the two blends PSA/PVME and PSS/PVME with linearly polarized uv light :[1] Upon irradiation, anisotropic phase separation takes place, giving lamella-like morphologies orienting almost perpendicular to the direction (E) of the linearly polarize light, For the photo-cross-linking systems, the phase separation proceeds faster along the direction perpendicular to (E), whereas it evolves fastest along the direction parallel I (E) for the photoisomerizing system.[2] All the irradiated blends exhibit different critical points at different orientation with respect to the polarization (E). The phase separation proceeds with different rates along different orientations. By comparing these kinetic data with the results obtained b irradiation with unpolarized light, it was found that the morphology emerging at a certain irradiation is the consequence of an interference process of different instabilities propagating along different orientations. Less