Langmuir, Vol.18, No.7, 2880-2887, 2002
Orientational ordering of structured polymeric nanoparticles at interfaces
Straight acrylic composite nanoparticles with a mean diameter of 132 nm and a mushroomlike particle morphology consisting of a soft poly(n-butyl acrylate) phase with a caplike poly(methyl methacrylate) hard phase covering one side of the particle were prepared by emulsion polymerization. The particles show oriented adsorption when deposited from a diluted dispersion as single particles onto flat substrates. On hydrophilic surfaces, the hard phase is preferentially oriented toward the substrate, whereas on hydrophobic substrates the soft phase is preferentially oriented toward the surface. Orientation at the film substrate interface and at the outer surface is also found when depositing dispersion films with thicknesses in the micron range. However, here the orientation does not change with the character of the surface and always the more hydrophobic soft phase is exposed. These findings are discussed in a framework of hydrophilic and hydrophobic interactions.