Collapse dynamics of copolymers in a poor solvent: Influence of hydrodynamic interactions and chain sequence

TL;DR

This study uses Brownian dynamics simulations to explore how hydrodynamic interactions and chain sequence affect the collapse process of copolymers in poor solvents, revealing that hydrodynamics aid collapse and sequence influences kinetics and final structure.

Contribution

It introduces a detailed simulation approach incorporating hydrodynamics and analyzes the impact of chain sequence on copolymer collapse dynamics.

Findings

Hydrodynamic interactions assist the collapse process.

Chain sequence significantly influences collapse kinetics.

Long P blocks slow down the formation of the globular state.

Abstract

We investigate the dynamics of the collapse of a single copolymer chain, when the solvent quality is suddenly quenched from good to poor. We employ Brownian dynamics simulations of a bead-spring chain model and incorporate fluctuating hydrodynamic interactions via the Rotne-Prager-Yamakawa tensor. Various copolymer architectures are studied within the framework of a two-letter HP model, where monomers of type H (hydrophobic) attract each other, while all interactions involving P (polar or hydrophilic) monomers are purely repulsive. The hydrodynamic interactions are found to assist the collapse. Furthermore, the chain sequence has a strong influence on the kinetics and on the compactness and energy of the final state. The dynamics is typically characterised by initial rapid cluster formation, followed by coalescence and final rearrangement to form the compact globule. The coalescence stage takes most of the collapse time, and its duration is particularly sensitive to the details of the architecture. Long blocks of type P are identified as the main bottlenecks to find the globular state rapidly.