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

本课题主要有两个目的：利用极化选择反应诱导各向异性相分离聚合物共混物；建立聚合物共混物形态控制的新方法。第一个目的是利用线偏振光选择性地诱导二元聚合物共混物组分之间的化学反应。这样，浓度波动的空间对称性被打破，导致各向异性相分离。为了阐明这种对称破缺过程对反应共混物形貌的影响，实验中采用了两种典型的反应，即交联反应和非交联反应。为了便于实验，本研究项目采用了具有较低临界溶液温度（LCST）的聚苯乙烯（P5）和聚乙烯甲基醚（PVME）的混合物。仅对PS组分进行了化学修饰，标记为花青素外消旋烯（PSA）或环二苯乙烯（PSS）。通过光二聚化蒽或光异构化PSS链上标记的苯乙烯基团，在PSA链间进行交联反应，使PS/P VME共混物失稳。用线偏振光照射PSA/PVME和PSS/PVME两种共混体系，得到了以下结果：[1]辐照后，发生了各向异性相分离，形成了几乎垂直于线偏振光方向(E)的片状形貌。而光异构化系统沿平行I (E)方向发展最快所有的辐照共混物在不同的取向上都表现出不同的临界点。相分离沿不同的取向以不同的速率进行。将这些动力学数据与非偏振光辐照得到的结果进行比较，发现在一定辐照下出现的形貌是不同不稳定性沿不同方向传播的干涉过程的结果。少

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