Arm retraction dynamics in dense polymer brushes

TL;DR

This study uses large-scale Monte Carlo simulations to analyze the relaxation dynamics of dense polymer brushes, revealing an exponential growth of relaxation time with chain length and unique entanglement effects.

Contribution

It provides a detailed quantitative analysis of the relaxation times in dense polymer brushes, highlighting the exponential dependence on chain length and entanglement effects.

Findings

Terminal relaxation time grows exponentially with chain length

Late time relaxation of perpendicular components is segment-independent

Entanglement degree of polymerization influences relaxation dynamics

Abstract

Large scale Monte Carlo simulations of dense layers of grafted polymer chains in good solvent conditions are used to explore the relaxation of a polymer brush. Monomer displacements are analyzed for the directions parallel and perpendicular to the grafting plane. Auto-correlation functions of individual segments or chain sections are monitored as function of time. We demonstrate that the terminal relaxation time $\tau$ of grafted layers well in the brush regime grows exponentially with degree of polymerization $N$ of the chains, $\tau\propto N^{3}\exp(N/N_{e})$, with $N_{e}$ the entanglement degree of polymerization in the brush. One specific feature of entangled polymer brushes is that the late time relaxation of the perpendicular component coincides for all segments. We use this observation to extract the terminal relaxation time of an entangled brush.