Explicit inclusion of the solvent molecules

Self-consistent Polymer Reference Interaction Site Model (PRISM) calculatio ns and molecular dynamics (MD) simulations were performed on athermal solut ions of linear polymers. Unlike most previous treatments of polymer solutio ns, we explicitly included the solvent molecules. The polymers were modeled as tangent site chains and the solvent molecules were taken to be spherica l sites having the same intermolecular potential as the polymer sites. The PRISM theory was solved self-consistently for both the single chain structu re and intermolecular correlations as a function of chain length and concen tration. The rms end-to-end distance from PRISM theory was found to be in a greement with corresponding MD simulations, and exhibited molecular weight dependence in accordance with scaling predictions in the dilute and concent rated solution limits. The presence of explicit solvent molecules had a sig nificant effect on the packing of the polymer by inducing additional struct ure in the intermolecular radial distribution function between polymer site s. Using the direct correlation functions from the athermal solution and th e random phase approximation, we were able to estimate the spinodal curves for solutions when polymer and solvent attractions were turned on. We found significant deviations from Flory-Huggins theory that are likely due to co mpressibility and nonrandom mixing effects. (C) 2001 American Institute of Physics.