New Method to Generate Reversible Hydrophobic and Hydrophilic Surfaces

Designer particles synthesized by surfactant-free emulsion polymerization were adsorbed successfully on the sapphire discs. The particles carried a thin layer of an atom transfer radical polymerization (ATRP) initiator on the surface and were subsequently successfully used to graft PNIPAAM brushes from the surface. The surface coverage of the discs by these particles could be improved by heat treatment of the discs which fused the particles with each other but keeping the initial ATRP layer on them. The reversible wetting characteristics of the surfaces as a function of temperature could be established by studying the behavior of water droplets placed on the PNIPAAM modified discs. The heat treated discs improved the reversible behavior further, though no superhydrophobic and superhydrophilic behavior could be achieved. The reversible temperature responsively makes these surfaces tremendously important for the commercial separation and filtration processes.