This award is under the Long and Medium-Term Research at Foreign Centers of Excellence Program, which enables U.S. scientists and engineers to conduct three to twelve months of research abroad at research centers of proven excellence. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twelve-month postdoctoral research visit by Dr. John M. Zielinski of Pennsylvania State University to work with Professor Doctor Hans Sillescu at the Institut fur Physikalische Chemie der Universitat Mainz. Knowledge of the diffusion rate is essential in designing adequate products for numerous applications including: (1) devolatilization, (2) medicinal time-controlled release, (3) drying of paints and coatings, (4) packaging or barrier membranes and (5) separation processes. Despite the importance of polymer/solvent diffusion coefficients, however, proportionately little data of this type are available in the literature, particularly at varying solvent concentrations. Due to the escalating emphasis on reducing emissions from commercial processes, diffusion studies of penetrant molecules in polymer systems at this time are warranted if not essential. Mutual-diffusion processes are inherently coupled to polymer and solvent self-diffusion and their thermodynamic interaction. The Pulsed Gradient Spin Echo (PGSE) nuclear magnetic resonance (NMR) technique and holographic grating have previously been employed to measure solvent self-diffusion coefficients. Only recently, however, have advances in instrumentation rendered these techniques viable for addressing polymer self-diffusion as well. Although acquiring data directly is extremely important, complementary theoretical studies are also required so that diffusional characteristics for polymer/solvent systems can be predicted a priori. The coupling of the self-and mutual coefficients is the weakest link in existing diffusion theories. Consequently, an indepth experimental and theoretical study of the relationship between the individual self-diffusion coefficients and the polymer/solvent mutual-diffusion coefficient is proposed. This award recommendation provides funds for a stipend for twelve months.
