Self-Organization of Polymer Films Using Single and Mixed Solvents on Chemically Patterned Surfaces

The breakup processes of polymer solution droplets deposited on chemically strip-patterned surfaces are investigated experimentally. Polystyrene is used as solute while various liquids are used as solvents. Breakup of the liquid film is found to progress by iterations of self-pinning on lyophilic channels and receding of the contact line on lyophobic channels. Accordingly, formation of the polymer thin film is incomplete when the contact lines are not pinned on the lyophilic channels, or when they are pinned on the lyophobic channels. To induce a Marangoni effect on breakup, binary solvent mixtures are used. For several mixtures, thin liquid films are elongated on the lyophilic channels, enhancing breakup. Such mixtures exhibit complete wetting on homogeneous lyophilic surfaces as a result of the Marangoni effect.