Chemical Engineering, Materials Science
University of Minnesota
We are pursuing a molecular-level understanding of polymer structure and dynamics. Currently, we are most interested in multicomponent systems — copolymers, homopolymer blends, and their mixtures — in solution and in the bulk state. Such materials are of great commercial interest, due primarily to the potential flexibility for tailoring superior combinations of physical properties. The overall scientific challenge is to understand how the thermodynamic interactions among the components control both structure and dynamics. For example, the (net) repulsive interactions between blocks of a block copolymer lead to spontaneous self-assembly into a variety of microstructures, each with a periodicity set by the molecular size, i.e., in the tens of nanometers. The same interactions may cause a blend of the corresponding homopolymers to undergo macroscopic phase separation. However, this separation is often quite slow, and may be arrested (e.g., by vitrification, crystallization, or added copolymer surfactant) to produce interesting morphologies with characteristic dimensions on the micron scale. In these, and other situations under study, the already distinctive dynamic properties of polymers may couple in unexpected ways to structural features.