Intermolecular Bonding and Microphase Separation in Multiblock Copolymers

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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.