Intelligent gel - Surface properties and functions of gels

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 Amonton's law F = muW, which well describes the friction of solids. The fri ctional force and its dependencies of on the load are quite different depen ding on the chemical structures of the gels, surface properties of the oppo sing substrates, and the measurement condition. The gel friction is explain ed in terms of interfacial interaction, either attractive or repulsive, bet ween the polymer chain and the solid surface. According to this model, the frictional is ascribed to the viscous flow of solvent at the interface in t he repulsive case. In the attractive case, the force to detach the adsorbin g chain from the substrate appears as friction. Surface adhesion between gl ass particles and gels measured by AFM showed a good correlation with the f riction, which support the repulsion-adsorption model proposed by authors.