Low Friction Using Immiscible Polymer Brush Systems

Within the NIC Research Group of JSC, Prof. Martin Müser and Dr. Sissi de Beer developed a method to reduce friction and wear between surfaces in relative sliding motion. The method is inspired by biological lubricants in which hydrophilic polymers keep an aqueous liquid from flowing out of the contact. The latter is the reason why - for example - human joints keep their lubricating properties at all times. Anchoring polymers to solid surfaces is an approach to mimic these biological lubricants: in good solvents, the polymers will swell and keep the solvent from flowing out of the contact.

A critical shortcoming of polymer brush lubrication is, however, that polymers on the opposing surfaces can interdigitate, which induces friction and wear. To prevent the latter, Müser reasoned that contacts between solvated hydrophilic and hydrophobic brushes would not interdigitate. Therefore, de Beer performed large-scale molecular dynamics simulations on JUGENE and JUQUEEN to show that employment of such asymmetric contacts between two different brushes, each of which prefers its own solvent, does indeed eliminate interdigitation of the polymers, which results in low friction and negligible wear. Experiments, which were performed in cooperation with Prof. Julius Vancso’s group at the University of Twente, confirmed the results.

More information can be found in the article “Solvent-induced immiscibility of polymer brushes eliminates dissipation channels” in Nature Communications (DOI: 10.1038/ncomms4781).
(Contact: Prof. Martin Müser, m.mueser@fz-juelich.de)