Entropy-driven polymer collapse: Application of the hybrid MC/RISM method to the study of conformational transitions in macromolecules interacting with hard colloidal particles

摘要

Self-consistent hybrid MC/RISM method is used for calculating properties of a linear polymer surrounded by colloidal particles with purely repulsive, hard-core, interactions between the particles and chain beads. Our approach combines the traditional atomistic Monte-Carlo (MC) simulation of flexible polymer chains with the numerical solution of the site-site Ornstein-Zernike-like (RISM) integral equations. Since the condensed-phase environment of a flexible macromolecule affects the equilibrium configuration probability distribution of the macromolecule, the site-site intramolecular correlation function and the intramolecular potential field are treated in a self-consistent manner. It is shown that in such an athermal system the medium-induced collapse of a polymer (similar to polymer collapse in a poor solvent) may occur. Our analysis yields a simple "entropic" interpretation of this transition. We present the detailed study of the dependence of conformational properties of the chains on the degree of polymerization, density and size of colloidal particles.