We describe the preparation and characterization of core-shell latex particles, consisting of a polystyrene core, covered with a perfluoroalkyl acrylate shell. The core-shell particles were prepared by a two-stage emulsion polymerization under kinetically controlled conditions and were characterized by transmission electron microscopy, differential scanning calorimetry, and X-ray diffraction analysis. The surface properties of the latex films produced from the core-shell particles were investigated by the contact angle method. Compared with random copolymers or latex blends of styrene and perfluoroalkyl acrylate, the core-shell particles were the most effective to reduce the surface energy of the latex films. The effect of acetone as a cosolvent on the polymerization process was also considered.

The surface properties of latex films prepared from heptadecafluorodecyl acrylate and 2,2,2trifluoroethyl methacrylate copolymers were investigated in terms of hydrophobicity and sliding behavior of liquid droplets. The hydrophobicity of fluorinated latex films evaluated from water contact angle was closely related to the chemical composition of the surface. On the other hand, the sliding angle of liquid droplets was not directly proportional to the hydrophobicity or oleophobicity of the latex films in the present study. Although the hydrophobicity of copolymer latex films was significantly enhanced by adding small amount of highly fluorinated heptadecafluorodecyl acrylate, it made water droplets rather difficult to slide down on an inclined surface. The sliding angle of water droplet was quite sensitive to the preparation methods, namely, batch and semicontinuous emulsion polymerizations in contrast to the hydrophobicity. The surface morphology and roughness of the latex films were found to be important to explain the observations.

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We report on the preparation of water-and oil-repellent surfaces using surface-attached monolayers of perfluorinated polymer molecules. A covalent attachment of the polymer molecules to the substrate surfaces is achieved by generation of the polymer chains through starting a surface-initiated radical-chain polymerization of a fluorinated monomer. To this, self-assembled monolayers of azo initiators are attached to SiO2 substrates, which are used to kick off the polymerization reaction in situ. The growth of the fluorinated polymer brushes and the characterization of the obtained surfaces by Fourier transform infrared spectroscopy, surface plasmon spectroscopy, X-ray photoelectron spectroscopy, and contact angle measurements is described. It is shown that perfluorinated polymer films can be grown with controlled thicknesses on flat and even on porous silica surfaces, essentially without changing the surface roughness. The combination of the low surface energy coating and the surface porosity allows generation of materials which are both water and oil repellent.

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SYNOPSISA poly (perfluoroalkylethyl methacrylate) and a series of poly (n-alkyl methacrylate) s such as poly (methyl methacrylate), poly (ethyl methacrylate), and poly ( n -butyl methacrylate) were prepared and used to investigate the surface properties of polymer mixtures containing a fluorinated homopolymer and a nonfluorinated homopolymer and the effect of the sidechain length of poly(n-alkyl methacrylate) on the surface free energy for the polymer mixtures. Contact angles were measured for the surfaces of polymer mixtures by varying the concentration of poly ( perfluoroalkylethyl methacrylate). From the contact angle data, it can be inferred that most of the poly (perfluoroalkylethyl methacrylate) added to poly ( nalkyl methacrylate) s is located in the outermost layer of polymer-mixture surface. Surface free energies for the outermost surfaces of polymer mixtures were calculated from the contact angle data using Owen and Wendt's equation. The decrease in the surface free energy for the polymer mixture with the poly (perfluoroalkylethyl methacrylate) addition is more pronounced as the side-chain length of poly (n-alkyl methacrylate) decreases. Due to the steric effect of the side chain of poly ( n -alkyl methacrylate), the arrangement of the perfluoroalkylethyl group of poly (perfluoroalkylethyl methacrylate) to the air side is considerably hindered. The ESCA analysis of atomic compositions of the surface for the polymer mixture verified that poly (perfluoroalkylethyl methacrylate) is preferentially arranged and concentrates a t the polymer mixture-air interface. The results of functional group compositions obtained by ESCA showed that the functional group composition of -CF3 for the outermost layer has a more important effect on the surface free energy than that of -CF2 -and confirmed the hindrance of the arrangement of perfluoroalkylethyl group to the air side by the side chain of poly( n-alkyl methacrylate).

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