Early Stages of Homopolymer Collapse

TL;DR

This paper presents a phenomenological model describing the early stages of homopolymer collapse after a temperature quench, highlighting droplet formation, growth, and bridge shortening with specific scaling laws.

Contribution

It introduces a new model for the kinetics of early homopolymer collapse stages, detailing the formation and growth of dense droplets and bridge dynamics.

Findings

Droplet formation occurs with minimal change in chain configuration.

Droplet growth involves monomer accretion from bridges.

Characteristic times scale with polymerization degree as 0, 1/5, and 6/5.

Abstract

Interest in the protein folding problem has motivated a wide range of theoretical and experimental studies of the kinetics of the collapse of flexible homopolymers. In this Paper a phenomenological model is proposed for the kinetics of the early stages of homopolymer collapse following a quench from temperatures above to below the theta temperature. In the first stage, nascent droplets of the dense phase are formed, with little effect on the configurations of the bridges that join them. The droplets then grow by accreting monomers from the bridges, thus causing the bridges to stretch. During these two stages the overall dimensions of the chain decrease only weakly. Further growth of the droplets is accomplished by the shortening of the bridges, which causes the shrinking of the overall dimensions of the chain. The characteristic times of the three stages respectively scale as the zeroth, 1/5 and 6/5 power of the the degree of polymerization of the chain.