Thermal-Induced Slippage of Soft Solid Films*

The dynamics of interfacial slippage of entangled polystyrene (PS) films on an adsorbed layer of polydimethylsiloxane (PDMS) on silicon was studied from the surface capillary dynamics of the films. By using PS with different molecular weights, we observed slippage of the films in the viscoelastic liquid and rubbery solid state respectively. Remarkably, all our data can be explained by the linear equation, J = -M▽P and a single friction coefficient, ξ, where J is the unit-width current, M is mobility and P is Laplace pressure. For viscous films, M is accountable by using conventional formulism. For rubbery films, M takes on different expressions depending on whether the displacements associated with the slip velocity, v_s (~▽P/ξ), dominate or elastic deformations induced by ▽P dominate. For viscoelastic liquid films, M is the sum of the mobility of the films in the viscous and rubbery states.