Project III – Relations between friction and adhesion in polymeric systems

Contributors: G.Reiter, M.Brendlé

This project is focused on the study of molecular energy dissipation mechanisms at polymer/polymer interfaces, which are responsible for both frictional and adhesive properties. Our approach is based on compatible or slightly incompatible polymers sliding past each other at model interfaces of controlled molecular parameters. For example, a crosslinked polydimethylsiloxane (PDMS) drop can be moved on solid substrates coated with grafted or adsorbed PDMS "monolayers". Parameters like the grafting density or crosslink density can easily be systematically varied. The rate dependence of both adhesion and friction will be studied in parallel or, whenever possible, even simultaneously.
The objective is to correlate these velocity effects to the intrinsic visco-elastic parameters of the studied polymers and to verify if friction and adhesion are governed by the same intrinsic viscoelastic parameters. A special focus will be on the transition between the static and the dynamic friction in relation to the extrapolated adhesive energy at infinitely small separation velocity.
The experimental realisation will be based on a simultaneously characterization of nano and macro contacts using techniques like AFM, macroscopic friction measurements, adhesion tests like JKR or tack measurements, dynamic wetting and dewetting studies or rheometric determination of viscoelastic properties.

Collaborations on the theoretical description of molecular energy dissipation mechanisms and on the application of our results obtained in fundamental studies to "real" systems found in technologically relevant systems are envisaged.