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.
