(495d) Dynamics of Semi-Flexible Polymers in a Poor Solvent

For polymers under poor solvent conditions, polymer chains form a compact globule, and the shape of the globule and conformation of the chain are sensitive to chain stiffness. While multiple studies of the dynamics and equilibrium conformations of such chains have been undertaken recently, to date no method of systematic coarse-graining such chains has been proposed.  In this study, we explore coarse-graining procedures for investigating the conformational and dynamic behavior of polymer chains with bending stiffness in poor solvent conditions using Brownian dynamics (BD) simulations. We study chains with fixed Kuhn length, but varying numbers of rods representing each Kuhn length, and seek conditions under which both static shear-flow properties of the collapsed configurations become insensitive to the degree of coarse-graining. We find conditions of solvent quality and chain stiffness under which coarse-graining leads to converged results, and where coarse-graining breaks down due to strong local interactions.  This method allows us to obtain general results for the effect of bending stiffness on the folding and unfolding of polymer chains under poor solvent conditions that are robust to the degree of chain resolution. We show that as chain stiffness increases, the collapse transition becomes steeper as solvent quality worsens, as does the unraveling transition that occurs under shearing flow.