The goal of this research is to understand the role of molecular and microstructural dynamics in determing the macroscopic material properties of polymers. In the case of polymeric liquids, they are combining experimental and theoretical approaches in order to advance our ability to predict their rheological properties. Due to the complex nature of these fluids, and in order to obtain appropriate information to test theory, it is necessary to observe the dynamics of individual components in multicomponent systems and to follow specific modes of relaxation in response to macroscopic deformation. To access this level of information, this research will be developing combined spectroscopic and rheometric methods to study the order-disorder transition in block copolymers, the rheology of miscible polymer melts, and the orientational order of rigid-rod polymer liquid crystals under flow. Molecular motions play an important role in solid polymers as well, and one aspect is the onset of mobility that is responsible for the broad glass transition characteristic of miscible polymer blends. Therefore, will be used solid-state deuterium nuclear magnetic resonance to observe the rate of molecular motion in each component of the blend individually as a function of temperature through the glass transition. These observations will give new insight into the factors that determine the temperature and breadth of the glass transition.
