Synthesis and pH-selective adsorption of latex particles onto photolithographically patterned silane layers.

Surface structures of charged latex particles on patterned surface layers were obtained by a colloidal self-assembly process. The laterally patterned silane layers were prepared on silica surfaces by vapor phase and solution deposition of silanes in combination with photolithography. The monodisperse latex particles used in the self-assembly experiments were synthesized by emulsion polymerization to yield poly-n-butylmethacrylate spheres (217 nm diameter) and poly-n-butylacrylate microgels (155 nm). Both particle types possessed a high surface concentration of free carboxylic acid groups as quantified by polyelectrolyte titration under shear flow. Depending on the pH, the particles assembled onto the hydrophobic surface regions (pH 9) or onto the hydrophilic regions (pH 5). Highest selectivity and pattern quality was obtained with permanently positively charged silane layers (quaternary ammonium salts) onto which the negatively charged colloid particles adhered strongly by Coulomb interaction.