Intermolecular Bonding and Microphase Separation in Multiblock Copolymers

这三个主要的研究方向旨在获得对多嵌段聚合物中相分离的定量理解。第一个方向旨在利用小角X射线散射(SAXS)、差示扫描量热法(DSC)和熔体流变仪来解决聚氨酯体系中的微相分离转变(MST)。将研究简化的聚氨酯系统，将硬段结晶和热降解引起的并发症降至最低。第二个方向是解决多嵌段聚合物的结晶问题。提出了一种研究结晶与MST关系的方法，该体系的MST可根据硬段熔点的不同而改变。本文还对聚醚-酯共聚物的结晶和陈化过程进行了SAXS研究，重点研究了熔融后重结晶过程中硬磁区形态的变化。与这些研究相辅相成的是旨在了解聚合条件对球晶织构发展的作用。第三个，也是最后一个研究方向是使用固态核磁共振技术来表征聚氨酯的形态。模型硬段化合物将用交叉极化/魔角旋转技术以C-13为探针核进行研究。这项工作将与质子核磁共振研究相辅相成，以了解硬域中特定位置的迁移率。这项工作将扩展到聚醚-聚氨酯共聚物，目的是表征界面区。

The three general directions of study are aimed at gaining a quantitative understanding of phase separation in multiblock polymers. The first direction intends to address the microphase separation transition (MST) in polyurethane systems using small- angle x-ray scattering (SAXS), differential scanning calorimetry (DSC), and melt rheometry. Simplified polyurethane systems will be studied which minimize complications due to hard segment crystallization and thermal degradation. The second direction addresses the problem of crystallization in multiblock polymers. A study of the relationship between crystallization and the MST is proposed using a polyurethane system whose MST may be altered relative to the hard segment melting point. A SAXS study of crystallization and annnealing processes in poly(ether-ester) copolymers is also proposed, emphasizing changes in hard domain morphology occuring during recrystallization after melting. Complementary to these studies is work aimed at understanding the role of polymerization conditions on spherulitic texture development. The third, and final direction of study is the use of solid-state NMR techniques to characterize polyurethane morphology. Model hard segment compounds will be investigated using cross polarization/magic-angle spinning techniques with C-13 as the probe nucleus. This work will be complemented with proton NMR studies in order to gain an understanding of site-specific mobilities in the hard domains. This work will be extended to polyether-polyurethane copolymers with an aim toward characterization of the interfacial regions.