Monte Carlo simulations of structures and dynamics of cyclic and linear poly(ethylene oxide) melts

Abstract

A lattice Monte Carlo (MC) simulation of coarse-grained polymer model was developed to study the conformation and diffusion of cyclic and linear poly(ethylene oxide), PEO, blends. Local intrachain interactions were derived from the modified rotational isomeric state (RIS) model and the non-bonded interactions were from a discretized form of Lennard-Jones (LJ) potential energy function. The simulations were performed at 373 K for the chain length from 50 to 200 repeating units. The relative size of linear/cyclic is 〈 R g 2 〉 linear / 〈 R g 2 〉 ring ∼ 2 which was consistent with the theoretical prediction. The diffusion coefficients of cyclic chains were higher than linear chains at high molecular weight. Lower diffusion coefficients of smaller cyclic polymers were attributed to the high local density within molecular volume. The sizes of linear and cyclic chains in binary blends were relatively unchanged at all composition. As the linear fraction increases, the diffusivities of both cyclic ( D C ) and linear ( D L ) decrease. In comparison, D C drops more than D L especially at longer chain length. The decrease in diffusivities was most pronounced at small concentration of linear fraction.