Superhydrophobic surfaces of microspheres obtained by self-assembly of poly[2-(perfluorooctyl)ethyl acrylate-ran-2-(dimethylamino)ethyl acrylate] in supercritical carbon dioxide

Superhydrophobic surfaces were obtained by coating with microspheres formed by the self-assembly of poly[2-(perfluorooctyl)ethyl acrylate-ran-2-(dimethylamino)ethyl acrylate] (P[POA-r-DAA]) in the presence of dicarboxylic acids in supercritical carbon dioxide. The P[POA-r-DAA] random copolymer aggregated into micellar microspheres through the hydrogen bond cross-linking of the amino groups via the carboxylic acids. The size of the microspheres and the amount of the acids needed to produce them were dependent on the kinds of acids. Glutaric acid (Glu) and perfluorosuccinic acid (Psuc) provided microspheres at a 0.5 molar ratio of the acid/DAA. Psuc produced smaller microspheres than Glu. Maleic acid (Ma), succinic acid (Suc), and azelaic acid (Az) required a higher molar ratio to produce the microspheres. These acids provided spherical particles at the ratio of 1.0. The microspheres produced by Suc and Az contained particles with a several hundred nanometer size. The surface coated with the microspheres showed high water contact angles of 164°–172°.