A nanoscale study of the adhesive contact

Analysis of adhesive and mechanical properties of model polymer surfaces can be achieved with an Atomic-Force Microscope (AFM), in contact mode. The purpose of this study is to dissociate the different contributions (chemical and mechanical) included in an AFM force-distance curve in order to establish relationships between interfacial tip-polymer interactions and surface viscoelastic properties of the polymer. Surface force measurements are, in a first step, done on chemically modified silicon substrates (grafted with hydroxyl, amine, methyl and ester functional groups). In order to investigate the effects of mechanical or viscoelastic contributions, force measurements on model polydimethylsiloxane (PDMS) networks, whose surfaces are chemically modified with the same functional groups as for silicon substrates, were achieved. New relationships are proposed between the local adhesion force and both the dissipation energy in the tip-polymer contact and the surface properties of the materials (thermodynamic work of adhesion). Moreover the dissipation function is related to M-c, the mass between crosslinks of the polymer network.