Kenneth S. Schweizer

Our overarching goal is the development and application of novel molecular-scale statistical mechanical theories of the equilibrium and dynamic properties of polymers, colloids, nanoparticles, liquid crystals, elastomers and other complex fluids and soft materials. A common theme is to both understand existing systems at a fundamental level and develop predictive methods for guiding the experimental design of new materials. Three broad areas are of present interest.

The structure of macromolecular liquids is sensitive to both the local chemical structure and global architecture of individual polymers, intermolecular forces and thermodynamic state. We are developing novel theories to predict the spatial organization and packing, statistical conformation, thermodynamics, phase behavior, elastic properties, and mechanical response of two broad classes of macromolecular materials : (i) particle-filled polymer nanocomposites, and (ii) strained melts, rubber networks and liquid crystals.

"Particle-polymer" suspensions are ubiquitous in diverse areas of science and technology . The spherical particle can be a micron-size colloid, a nanoparticle, globular protein or self-assembled micelle. How polymers influence the spatial structure, phase behavior, and viscoelastic properties of such suspensions is of importance in organic and ceramic materials science, colloid science, and biology. The presence of multiple forces (van der Waals, excluded volume, electrostatic, particle coating), variable solvent conditions, and particle/polymer size disparities results in a very rich physical behavior. We are developing new theories to predict the properties of such systems, including the subtle competition between gelation, crystallization and phase separation, structural reorganization in sticky particle suspensions, and the role of polymer rigidity, polymer-particle adhesive interactions and other chemically specific effects. The equilibrium and dynamic behavior of suspensions composed of nonspherical particles, such as a discotic nanoparticles, nanotubes and fractal aggregates, are also of interest.

A broad area of enduring interest is the slow dynamics of complex fluids. Our goal is the development and application of statistical dynamical theories formulated at the level of intermolecular forces. Present work is focused in three areas : (i) glass transition and transport properties in colloidal and nanoparticle suspensions, polymer melts and molecular liquids, (ii) gelation and viscoelasticity of particle suspensions and soft solids, and (iii) diffusion and glass formation in anisotropic and/or geometrically confined polymer melts . All the dynamics work is closely coupled with the equilibrium efforts to establish molecular-level connections between structure and time-dependent properties.