Interfacial friction between semiflexible polymers and crystalline surfaces

TL;DR

This study uses molecular dynamics simulations to explore how semiflexible polymer chains interact with crystalline surfaces, revealing a maximum in friction at low slip velocities due to shear-induced chain alignment.

Contribution

It introduces a detailed analysis of how chain stiffness affects interfacial friction and slip behavior in polymer melts near crystalline surfaces.

Findings

Friction coefficient peaks at low slip velocities due to chain alignment.

At high slip velocities, friction becomes independent of chain stiffness.

The study links chain structure to shear rate-dependent slip length behavior.

Abstract

The results obtained from molecular dynamics simulations of the friction at an interface between polymer melts and weakly attractive crystalline surfaces are reported. We consider a coarse-grained bead-spring model of linear chains with adjustable intrinsic stiffness. The structure and relaxation dynamics of polymer chains near interfaces are quantified by the radius of gyration and decay of the time autocorrelation function of the first normal mode. We found that the friction coefficient at small slip velocities exhibits a distinct maximum which appears due to shear-induced alignment of semiflexible chain segments in contact with solid walls. At large slip velocities the decay of the friction coefficient is independent of the chain stiffness. The data for the friction coefficient and shear viscosity are used to elucidate main trends in the nonlinear shear rate dependence of the slip length. The influence of chain stiffness on the relationship between the friction coefficient and the structure factor in the first fluid layer is discussed.