The role of lubricant molecular shape in microscopic friction

TL;DR

This study uses a 2D model to explore how the shape and sticking properties of linear molecules in a lubricant film affect microscopic friction, revealing that longer chains and single-termination molecules tend to increase friction.

Contribution

It introduces a simple 2D simulation model to analyze the impact of molecular shape and sticking behavior on microscopic friction in lubricants.

Findings

Friction increases with chain length, correlating with bulk viscosity.

Molecules with a single sticking termination generally produce higher friction.

The model aligns with experimental observations of soft-lubricant regimes.

Abstract

With the help of a simple two-dimensional model we simulate the tribological properties of a thin lubricant film consisting of linear (chain) molecules in the ordinary soft-lubricant regime. We find that friction generally increases with chain length, in agreement with their larger bulk viscosity. When comparing the tribological properties of molecules which stick bodily to the substrates with others carrying a single sticking termination, we find that the latter generally yield a larger friction than the former.