Arun Yethiraj is supported by a CAREER grant from the Theoretical and Computational Chemistry Program to perform theoretical studies of the static and dynamic properties of polyelectrolyte solutions. The conformational properties of the polyelectrolyte molecules in dilute solution will be investigated as a function of ionic strength. The predictions of the theory will first be tested against molecular simulations for a simple model. The theory will then be used to investigate the conformational behavior of a chemically realistic model for polyacrylic acid. Simulations of two-molecule systems that incorporate the rest of the solution via site-site solvation potentials will be performed in order to estimate the importance of intermolecular interactions in polyelectrolyte solutions. These simulations will also be used to interpret light scattering experiments on polyelectrolyte solutions. Finally, single chain and two-molecule Brownian dynamics simulations will be performed in order to investigate the viscosity and self-diffusion coefficient as a function of ionic strength. Yethiraj's teaching goals at the undergraduate level include: 1) promoting in-class discussions; 2) promoting group learning; and 3) computer aided instruction. In graduate level courses he will introduce computational techniques ranging from ab initio and semi-empirical methods in quantum chemistry to Monte Carlo and molecular dynamics simulations of classical systems. Polyelectrolytes are charged macromolecules. They display a richer variety of properties than neutral polymers, and they have a wide range of technological uses, for example: as flocculants, dewatering agents, demulsifiers, and drag reduction agents; as additives in detergents and cosmetics; and in the manufacture of membranes, ion-exchange resins, gels and modified plastics. The behavior of polyelectrolytes, however, is far from well understood, and there has recently been an increased interest in obtaining a better molecular level understanding of these systems. Yethiraj's research will help to elucidate those molecular properties which are important in achieving desired materials properties for polyelectrolyte systems.
