Molecular dynamics study of the effect of solvent types on the dynamic properties of polymer chains in solution

Abstract

The effect of types of solvent on the dynamic properties of atactic poly(methyl methacrylate)s (a-PMMA)s chains in solution was studied by a molecular dynamics simulation technique with the condensed-phase optimized molecular potentials for atomistic simulation studies (COMPASS) force field. Five kinds of casting solvent molecules were randomly embedded into the a-PMMA matrix to construct various types of simulated a-PMMA solutions based upon experimentally obtained densities. The dynamic properties of polymer chains such as mean-square end-to-end distance < R 2 >, mean-square radius of gyration < S 2 >, and asphericity ratio < R 2 >/< S 2 > of polymer chains were analyzed. Simulated results revealed that the < R 2 > of the a-PMMA chains increased with the increase of the dipole moment of the surrounded solvent molecules. The asphericity ratio of polymer chains showed a high correlation to the molecular weight of solvents. Furthermore, the simulated radial distribution function of H-H atomic pairs in the system of a-PMMA solutions indicated that the expansion of a polymer chain depends mainly on the conformation of solvent molecules instead of the interaction between the polymer chain and the functional group on solvent molecules.