Sliding Friction at a Rubber/Brush Interface

TL;DR

This study investigates the frictional behavior of PDMS rubber sliding over a substrate with tethered PDMS chains, highlighting the role of chain pull-out and relaxation mechanisms in interfacial dissipation.

Contribution

It provides experimental evidence supporting the arm retraction relaxation model for chain-mediated friction at a rubber/brush interface.

Findings

Friction stress depends on sliding velocity, grafting density, and molecular weight.

Pull-out of tethered chains significantly contributes to interfacial dissipation.

Results support the arm retraction relaxation model for chain dynamics in friction.

Abstract

We study the friction of a poly(dimethylsiloxane) (PDMS) rubber network sliding, at low velocity, on a substrate on which PDMS chains are end-tethered. We thus clearly evidence the contribution to friction of the pull-out mechanism of chain-ends that penetrate into the network. This interfacial dissipative process is systematically investigated by probing the velocity dependence of the friction stress and its variations with the grafting density and molecular weight of the tethered chains. This allows us to confirm semi-quantitatively the picture of arm retraction relaxation of the grafted chains proposed in models of slippage at a network/brush interface.