Dissipation of polymer brushes

Lubrication of biological systems often involves the presence of polymers that are end-anchored to rubbing surfaces. The polymers swell in a solvent to form brushes, which then act as low-viscosity bearings when surfaces slide against a counter face.

In a recent article, featured on the cover of Soft Matter and picked as one of July’s hot papers by RSC, we investigated a commonly assumed hypothesis: Friction between rubbing surfaces is predominantly induced by the mutual penetration of opposing polymer brushes.

Our computer simulations revealed that the established opinion is only correct for conformal or related geometries. Including surface roughness, we found that losses due to viscoelastic deformation of polymer brushes as well as capillary hysteresis are leading-order dissipation mechanisms. Currently, we are investigating how these insights can be exploited to further improve the properties of polymer-brush-based tribo systems.

Reference:
S. de Beer and Martin H. Müser, Alternative dissipation mechanisms and the effect of the solvent in friction between polymer brushes on rough surfaces,
Soft Matter (2013) 9, 7234-7241
DOI: 10.1039/C3SM50491C