Wetting of polymer covered surfaces

Abstract

We consider solid surfaces, partly covered with flexible, neutral, linear polymers (by adsorption or by grafting), wetted by a liquid which is a good solvent of the poymer. We give formulae for the spreading coefficient S as a function of chain length, solvent quality and adsorption strength. We also discuss the wetting films obtained in spreading a droplet of (non volatile) solvent : the equilibrium thickness e of the film is a compromise between S (favouring thin films) and the coil entropies (favouring thick films) : in most cases e is rather small. Finally we analyse the spreading on certain « patchy » coatings where the film thicknesses can change dramatically with time