Surface friction of polymer gels 1. Effect of interfacial interaction

The sliding friction of various kinds of hydrogels has been studied and it was found that the frictional behaviors of the hydrogels do not conform to Amontons' law, F = muW, that well describes the friction of many solids. Th e frictional force and its dependencies of on load are quite different depe nding on the chemical structures of the gels, surface properties of the opp osing substrates, and the measurement condition. The gel friction is explai ned in terms of interfacial interaction, either attractive or repulsive, be tween the polymer chain and the solid surface. According to this model, fri ction is ascribed to the viscous flow of solvent at the interface in the re pulsive case. In the attractive case, the force to detach the adsorbing cha in from the substrate appears as friction. Surface adhesion between glass p articles and gels measured by AFM showed a good correlation with the fricti on, which support the repulsion-adsorption model proposed by the authors. ( C) 2001 Elsevier Science B.V. All rights reserved.