9424472 Ediger The local segmental dynamics of a given chain are determined by chemical structure, intramolecular potentials, and the chain's environment. Optical experiments, NMR experiments, and molecular dynamics computer simulations will be performed to investigate these aspects of local dynamics in polymer solutions, melts, blends, and glasses. One project will utilize molecular dynamics computer simulations to investigate whether Tg is related to the extent of cooperative motion which occurs in response to a conformational transition. Simulations are an ideal tool to understand the microscopic features of local polymer motion when they are tested by experiments which allow an assessment of realism. A second project will use a recently developed photobleaching technique to explore the molecular origins of physical aging. Physical aging causes degradation of the properties of glassy polymers over time. These experiments will also help to unravel the fundamental nature of the glass transition in polymers. A third project will use low-field NMR spectroscopy to study how the two components of a polymer blend influence each other's local dynamics. These influences determine the mechanical properties of the blend. Ultimately, a prediction of blend properties from component properties may be feasible. %%% Local polymer dynamics play an important role in the structure/property relationships of amorphous polymers. Local dynamics are directly responsible for a number of important polymer properties such as the glass transition temperature and the temperature dependence of the viscosity. A fundamental understanding of local polymer dynamics may allow the modification of existing materials to enhance specific properties and possibly the development of new materials. ***
