Dynamic Processes in Glassy Polymers

9412929这项工作是雅各布·谢弗教授领导的实验小组和罗伯特·雅里斯教授指导的理论小组之间的合作成果。该实验小组开发了使用固态核磁共振精确测量聚碳酸酯中标记原子之间的链间距离的新方法。在这一授权期内，我们将测量额外的链间距离，以进一步表征聚碳酸酯玻璃态的结构。此外，我们还将研究聚碳酸酯与衍生聚碳酸酯的共混，以研究其动态行为的变化。这项工作还将与聚碳酸酯及其共混物的力学性能的动态力学研究相结合。该理论小组开发了一种通用方法来模拟系统的长期动态，并将其应用于聚碳酸酯的简化模型。在这一授权期内，我们将使用从实验组获得的约束和参数，分几个步骤将这种模拟扩展到聚碳酸酯本身。玻璃聚合物(塑料)是非常重要的工业原料。特别是，聚碳酸酯具有非常不寻常的物理性质--它是子弹状的玻璃。我们正在研究它，以表征和了解它的分子动力学性质。研究和建模的长期目标是了解聚合物玻璃的微观动力学和它们的宏观物理性质之间的联系。

9412929 This work is a collaborative effort between an experimental group under the direction of Professor Jacob Schaefer and a theoretical group under the direction of Professor Robert Yaris. The experimental group has developed new methods using solid-state nuclear magnetic resonance to accurately measure interchain distances between labeled atoms in polycarbonate. In this grant period we will measure additional interchain distances to further characterize the structure of the glassy state of polycarbonate. In addition, we will study blends of polycarbonate with a derivitized polycarbonate to study the changes in dynamic behavior. This work will also be combined with dynamic mechanical studies on the mechanical properties of polycarbonate and the blends. The theoretical group has developed a general method to simulate the long-term dynamics of a system and has applied this to a simplified model of polycarbonate. In this grant period we shall extend this simulation, in several steps, to polycarbonate itself using constraints and parameters obtained from the experimental group. %%% Glassy polymers (plastics) are very important industrial materials. In particular, polycarbonate has very unusual physical properties -- it is bulletprooof glass. We are studying it in order to characterize and understand its molecular dynamic properties. The long-range goal of the study and modeling is to develop an understanding of the connection between the microscopic dynamics of polymer glasses and their macroscopic physical properties.