Ultrastructural Studies of Polymers

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This research deals with two areas of polymer materials research (1) phase transitions, morphology, and properties of block copolymers; and (2) high-resolution electron microscopy (HREM) of crystalline polymers. The first area involves the detailed study of neat linear and star diblock copolymers and block copolymer/homopolymer blends as concerns order-disorder transitions and order-order transitions. Emphasis will be placed on understanding the molecular parameters which govern phase morphology and stability. Both small and especially large-strain mechanical behavior of these model ordered microcomposites will be examined and related to the evolution of domain morphology with extent of deformation. The word in HREM will focus on understanding the details of chain packing in flexible chain-folded crystals particularly as regards regions where the chain arrangement reflects fundamental information on crystal growth (primary nucleus, twin boundaries, reentrant growth fronts). The main investigative techniques are transmission electron microscopy diffraction, small-angle x-ray scattering, digital image analysis, computer graphics of surfaces and mechanical testing. The goal of the research is to contribute to the basic understanding of structure-property relationships which can provide a basis for development of materials and improvement of their properties.