Robert Pecora is supported by a grant from the Theoretical and Computational Chemistry Program to continue his research involving motions in liquid and polymer systems. A variety of light scattering techniques are used such as Fabry-Perot interferometry and photocorrelation spectroscopy as well as total intensity light scattering and transient electric birefringence decay. The dynamics of both dilute and nondilute solutions of rigid and semirigid rodlike molecules including polypeptides, collagen, small rodlike protein, oligonucleotides, and DNA fragments will be studied. The effect of interaction and entanglement will be investigated, and the nature of slow modes will be elucidated. A model composite liquid has been developed which consists of small coated silica spheres and a rigid polymer immersed in a solvent. This system will also be studied by dynamic light scattering and transient electric birefringence decay. Composite liquids are a ubiquitous class of materials which contain polymer, particles and solvent. They are used as ceramic precursors, lubricants, paints and coatings, adhesives, and in chromatographic columns. Due to their complexity and the lack of adequate model systems, the interactions between the species in such systems are not well understood. Pecora has constructed a model rod/sphere composite liquid whose dynamics can be studied over a wide range of composition of both the rods and the spheres using an experimental technique known as dynamic light scattering.
