Dimensions of a Polymer Chain in a Mixed Solvent

Abstract

The equilibrium behavior of a flexible polymer in a binary solvent mixture is investigated via Monte Carlo simulation. The mixed solvent is modeled as an Ising fluid occupying the sites of a simple cubic lattice, with the polymer described as a self-avoiding random walk on the same lattice. The solvent has a critical consolute point, and the polymer preferentially adsorbs the better solvent component. A coupling between preferential adsorption and the solvent correlations present near the consolute temperature of the solvent causes the chain to contract, as predicted by Brochard and de Gennes. However, preferential adsorption also causes chain contraction far from the critical temperature. At large values of preferential adsorption, the chain contracts below the dimensions it would have in either of the pure solvent components. © 1988, American Chemical Society. All rights reserved.