Adhesion on Nanoorganized Multilayers: Surface Thermodynamics and Local Energy Dissipation

Abstract

Nanostructured multilayers, composed of alternate organic (3-mercaptopropyltrimethoxysilane, alkylthiols, polydimethylsiloxane) and metallic (gold) layers, are grafted onto glass and prepared in order to modify the mechanical and dissipative properties of a thin surface layer of the substrate. The external face is constituted either of gold or alkyl groups, allowing us to study two types of surfaces exhibiting different chemical and thermodynamic properties. The formation and the structure of the nanostructured multilayers are first examined by means of various techniques such as atomic force microscopy (AFM), wettability, X-ray photoelectron spectroscopy (XPS), and conductivity measurements. All the results concerning the structure of the systems studied are used to understand the adhesive properties at short contact times (tack) of the multi-layers and an elastomer (polyisoprene). The influence of the structural aspects of gold layers, the length of the alkyl chains of the top layer, the terminal functionality, and the length of the confined organic layer between two gold layers on the energy of adhesion regarding the polyisoprene are clearly demonstrated. The influence of the nano-structured surface layers on adhesion phenomena is explained in terms of either the surface thermodynamics or local energy dissipation during the propagation of a fracture according to complex mechanisms.