Polymer nanocomposite coatings with non-linear elastic response

We fabricated polymer nanocomposite layered coatings with distinguished, non-linear nanomechanical behavior. The tri-layer film, with a total thickness of 20–30 nm, was composed of a hard topmost layer of a cross-linked poly(dimethacrylate), a compliant rubber interlayer, and a self-assembled monolayer chemically tethered to a silicon substrate. Nanometer scale deformation of this coating produced a non-linear elastic response with high initial resistance followed by more compliant behavior before higher resistance showed up again in highly compressed (about 60% of initial thickness) state. Deformation of the film was completely reversible due to the properties of the rubber interlayer and the grainy microstructure of the topmost layer. Such non-linear surface behavior is quite unique and brings a new prospective in the design of organized surfaces with tailored nanomechanical response.