REFERENCE INTERACTION SITE MODEL-THEORY OF POLYMERIC LIQUIDS - SELF-CONSISTENT FORMULATION AND NONIDEALITY EFFECTS IN DENSE SOLUTIONS AND MELTS

The reference interaction site model (RISM) integral-equation approach to polymeric liquids is generalized to allow a self-consistent determination of single-chain and intermolecular pair correlations. Nonlinear medium-induced effects on intrachain statistics are described at the level of self-consistent pair interactions. Tractable schemes to implement the self-consistency aspect are formulated for semiflexible and rotational isomeric state chain models, and applied numerically to concentrated solutions and melts of semiflexible polymers. Theoretical results are in good agreement with off-lattice molecular dynamics simulations, and a rich dependence of the renormalized persistence length on temperature, aspect ratio, density, and degree of polymerization is found. The general formalism for polymer alloys is sketched and the potentially important role of local density and concentration fluctuations as nonuniversal mechanisms for inducing conformational perturbations is emphasized. A detailed analysis is made of the connections between the polymer RISM integral-equation theory and the field theoretic psuedopotential formalism, and remarkable similarities in the predictions of the two distinct approaches for solutions of long thread-like polymers are demonstrated.