Novel self-organization of polymer particles on hydrophobic solid surfaces through hydrophobic interaction

A novel technique of particle monolayer fabrication based on hydrophobic interactions in aqueous systems is described in this paper. When alkylated glass plates modified with various silane coupling agents were immersed in aqueous dispersions of submicron-sized polystyrene particles of cationic or anionic surface charges, cationic particle monolayers containing active ester groups were effectively formed at the plate surfaces, whereas no anionic particles were self-organized on the plate surfaces. The coverage of the plates with cationic particles and the morphology of the monolayers varied with the hydrophobicities of the particles and plates as well as with the ionic strength of the medium and temperature. For less hydrophobic methylated glass surfaces modified with methyltriethoxysilane, cationic particles were self-organized at relatively regular intervals, whereas they were self-organized in the form of aggregates for the more hydrophobic octadecylated glass plates treated with n-octadecyltriethoxysilane. Closely packed monolayers were fabricated by adjusting ionic strength and temperature. Fluorescence labelling of cationic particle monolayers was successfully accomplished by the reaction of remaining active ester groups on the monolayers with a fluorescence probe containing amino groups. Cationic particle monolayers were physically stabilized by heating above the glass transition temperature (T-g) of the particles.