This project comprises several investigations. Emphasis recently has been on studies of the structure and dynamics of dense macromolecular systems. For example, theoretical models have been used to study the geometrical and topological characteristics of disordered or irregular media such as gels and branched polymers. Analytical methods and Monte Carlo simulations have been developed to study the fractal dimensionality, conductivity, and diffusion exponents of those models. In a related activity, computer simulations of the escape of drug molecules from the surface pores of encapsulated polymer matrices have been performed and analyzed. Relationships have been determined for the rate of release as a function of the dimensionality and size of the matrix and uncoated surfaces. Small angle neutron scattering (SANS) studies have been performed, in collaboration with scientists at the National Bureau of Standards and the Massachusetts Institute of Technology, to determine interactions and structural ordering between macromolecules in dense solutions of biopolymers. Computer-based procedures for deducing intermolecular forces from experimentally determined structure factors have been developed. The variation of macromolecular surface charge occurring when solution properties are changed has been investigated in samples containing as much as 20 percent wt/vol protein.
