Intermolecular Bonding and Microphase Separation in Multiblock Copolymers

研究的三个主要方向是为了获得对多嵌段聚合物相分离的定量理解。第一个方向是利用小角度x射线散射（SAXS）、差示扫描量热法（DSC）和熔体流变法研究聚氨酯体系中的微相分离转变（MST）。简化聚氨酯系统将研究，以尽量减少由于硬段结晶和热降解的并发症。第二个方向解决了多嵌段聚合物的结晶问题。提出了一个研究结晶和MST之间的关系，使用聚氨酯体系，其MST可以相对于硬段熔点而改变。本文还对聚醚-酯共聚物的结晶和退火过程进行了SAXS研究，重点研究了熔融后再结晶过程中硬畴形貌的变化。与这些研究相辅相成的是旨在了解聚合条件对球粒织构发育的作用的工作。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。模型硬段化合物将以C-13为探针核，采用交叉极化/魔角旋转技术进行研究。这项工作将与质子核磁共振研究相辅相成，以获得对硬域中特定位点迁移的理解。这项工作将扩展到聚醚-聚氨酯共聚物，目的是表征界面区域。

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.