Nanotribological behavior of tethered reinforced polymer nanolayer coatings

We fabricated molecularly thick thermoplastic elastomeric films with organized microdomain structure and intriguing nanotribological properties. Molecular films from poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) were obtained by a melt/solution grafting to a functionalized silicon surface modified with epoxy-terminated self-assembling monolayers. We varied the thickness of grafted block–polymer films from 1.35 nm (disordered polymer layer) to 9 nm (well defined nanophase structure) and tested their friction, adhesion, shear and wearing properties on a microscale with scanning probe microscopy. Tethered SEBS monolayers, composed of a rubber matrix reinforced by a two-dimensional net of glassy polystyrene (PS) microdomains, possess a friction coefficient as low as 0.02 and shear strength in the range 0.15–1.5 GPa. Chemically tethered SEBS monomolecular films are much more stable under shear stresses than conventional molecular coatings.