FRG: Single-Molecule Spectroscopy Studies of Polymer Melt Rheology

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This award describes a program of research aimed at applying single-molecule spectroscopy to problems in tbe dynamics and rheology of polymer melts. This will be accomplished through a collaboration of three research groups: Waymouth (synthesis), Moerner (single-molecule spectroscopy), and Fuller (rheology). The outcome of this research will provide direct measurements of orientation and translation of single monomer units attached to polymer chains at strategic locations. Liner chains, tagged with fluorophores at the ends or at the center, will be studied. Star and H-shaped chains will also be considered to understand the consequences of long chain branching. These branched architectures will either be tagged an the ends or arms, or at the branched points.The dynamics of quiescent melts, or of melts subjected to either simple shear flow or extensional flow will be measured. These data will offer the first direct measurements of orientation dynamics and translation of individual polymer segments. The ability to track orientation and translational fluctuations of entangled segments is important to understanding the process of tube renewal and constraint release.The high level of multidisciplinary integration and collaboration in this project will provide a valuable and stimulating educational environment for graduate students. In addition, this research program will provide new information about the fundamental behavior of entangled polymer melts, which will be useful in the broader contexts of melt flow processing and extrusion.