Fundamental studies of the structure and dynamics of viscoelastic liquids are being carried out using dynamic light scattering. Fluctuations in the positions and orientations of molecules give rise to light scattering. Analysis of the power spectrum and time dependence of the scattered light leads to the understanding of the nature and time scale of molecular motion in liquids. The full distribution of relaxation times associated with liquids is determined.
The structure and dynamics of polymer solutions is being studied using photon correlation spectroscopy. In dilute solution, the overall shape and the translation and rotational diffusion coefficient are measured. If the polymer molecules are large enough, intramolecular motions are studied as well. Polymer molecules pervade the entire solution at very small overall concentrations. We are studying the structure and dynamics of polymer solutions where the molecules are overlapped.
The nature and dynamics of the glass transition in polymers is being studied using light scattering spectroscopy and calorimetry. The influence of geometric structure including the formation of polymer networks is being determined. The full distribution of relaxation times near the glass transition is determined.
The structure and dynamics of supercoiled DNA is being studied using static and dynamic light scattering. Both overall motion and intramolecular motion are being measured.
Nonlinear optical materials are key components in the integrated optical devices used in information processing. Polymeric materials have important mechanical and processing advantages over traditional inorganic crystals. We are studying the nonlinear optical properties of polymeric materials. A multidisciplinary approach involving synthesis, processing, measurements and theoretical calculations is employed.