Dynamics of partial wetting and dewetting of an amorphous fluoropolymer by pure liquids

We report velocity dependencies of dynamic contact angles for CCl4 and tert-butyl alcohol on the amorphous fluoropolymer AF 1600 and compare them with our previous results for octamethylcyclotetrasiloxane (OMCTS) on the same substrate. The molecules of these liquids have well-defined form and the solid surface is almost smooth and homogeneous, which enables checking the assumptions of the main theories of wetting dynamics. We find that the molecular-kinetic theory well represents the data for CCl4 in the characteristic cos ϑ/V scale but qualitatively disagrees with the experiment for tert-butyl alcohol and OMCTS at high velocities. The CCl4 data do not fulfill the requirement of the hydrodynamic theory for symmetric advancing and receding branches. For the other two systems, the hydrodynamic theory works better at high velocities, but the nonlinear initial sections of the ϑ3/V plots require consideration of the velocity dependence of the microscopic dynamic contact angle ϑc(V). This is done by the molecul...