Long and Medium-Term Research: Studies of the Effect of Polymer/Solvent Self-Diffusion and Thermodynamics Coupling on Mutual-Diffusion

该奖项是根据外国卓越中心长期和中期研究计划颁发的，该计划允许美国科学家和工程师在国外公认的卓越研究中心进行为期3至12个月的研究。该项目的奖项提供了联合研究的机会，并提供了使用国外独特或互补的设施、专业知识和实验条件的机会。该奖项将资助宾夕法尼亚州立大学约翰·M·齐林斯基博士为期12个月的博士后研究访问，与美因茨皮草物理化学学院的汉斯·西列斯库教授合作。了解扩散速率对于设计适用于多种应用的适当产品至关重要，这些应用包括：(1)去挥发，(2)药物时间控制释放，(3)油漆和涂层干燥，(4)包装或阻隔膜和(5)分离过程。然而，尽管聚合物/溶剂扩散系数很重要，但文献中提供的此类数据相对较少，特别是在不同溶剂浓度下。由于对减少商业过程排放的重视程度不断提高，此时渗透分子在聚合物体系中的扩散研究即使不是必要的，也是必要的。互扩散过程本质上与聚合物和溶剂的自扩散及其热力学相互作用相耦合。脉冲梯度自旋回波(PGSE)、核磁共振(核磁共振)技术和全息光栅已被用来测量溶剂的自扩散系数。然而，直到最近，仪器设备的进步才使这些技术也可以用于解决聚合物的自扩散问题。虽然直接获取数据非常重要，但还需要进行补充的理论研究，以便能够预先预测聚合物/溶剂体系的扩散特性。自系数和互系数的耦合是现有扩散理论中最薄弱的一环。因此，本文对聚合物/溶剂互扩散系数与个体自扩散系数之间的关系进行了深入的实验和理论研究。这项奖励建议为12个月的津贴提供资金。

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.