Sliding Friction of Polymers: The Complex Role of Interface

The objective of this work is to analyse the influence of interfacial properties on the sliding friction of polymers. In order to change the nature of interface, two types of smooth and rigid substrates are used: a hydrophilic silicon wafer (hydroxylated by a piranha treatment) and a hydrophobic silicon wafer, obtained by a chemical grafting with a CH₃ terminated silane. Both substrates exhibit identical stiffness and roughness and differ only by their surface chemical composition. Two different polymers are studied: crosslinked polydimethylsiloxane, PDMS (soft elastomer with a low glass transition temperature) and polystyrene (rigid thermoplastic polymer with a high glass transition temperature). Friction experiments are performed with a translation tribometer for different normal forces and friction speeds.