Specific Interactions In Polymer Systems

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TECHNICAL SUMMARYThis research involves studies of specific interactions in polymer systems. One part of the proposed work seeks to obtain a fundamental understanding of the interplay between microstructure and the fraction of same chain contacts, or self-concentration, in hydrogen bonded polymer blends. Measurements of the fraction of hydrogen-bonded groups in these mixtures will also be used to determine the effect of hydrogen bonding on rheological properties. This work will be complemented by the second part of the proposed research, which involves studies of the shapes and widths of bands in these strongly interacting systems and how these are affected by interactions and relaxation processes. Infrared bands and Raman lines are sensitive to local environment and picosecond scale dynamics. The extent to which useful information can be obtained from the spectra of polymers will be evaluated by comparing the results of band shape analysis to those obtained by applying ultrafast two-dimensional infrared spectroscopic (2D-IR) techniques. NON-TECHNICAL SUMMARYThe factors that govern both the mixing of polymer materials and so-called relaxation phenomena (which govern their mechanical and rheological behavior) is of considerable practical importance. Finding polymers that mix at the molecular level (most do not) can lead to materials with novel properties. Even polymers that phase-separate can have important properties, such as enhanced impact resistance, providing that the size of the phase separated domains are controlled. This research will use infrared spectroscopy to study both specific interactions and relaxation behavior in polymers and their mixtures. The work will also contribute to education through the mechanism of involving both undergraduate and graduate students in laboratory work, thus teaching them the fundamentals of spectroscopic and other techniques. More uniquely, work supported on previous NSF awards that resulted in CD based monographs, complete with animations and interactive programs, will be extended to produce sets of lectures that will be freely accessible over the web.