Photoreactive composite coating with composition dependent wetting properties

Abstract

Photoreactive composite thin layers with tunable wetting properties from superhydrophilic to superhydrophobic nature were prepared. To achieve extreme wetting properties, the adequate surface roughness is a crucial factor, which was achieved by the incorporation of plasmonic Ag-TiO2 particles, as polymer filler, into the smooth polymer film with adjusted hydrophilicity. The initial copolymer films were synthesized from hydrophilic 2-hydroxyethyl-acrylate (HEA) and hydrophobic perfluorodecyl-acrylate (PFDAc) monomers. In the case of hydrophobic PFDAc, the photocatalyst-roughened thin films displayed superhydrophobic behavior (gamma(tot)(s) similar to 2.3 +/- 1.7 mJ/m(2), Theta > 150 degrees), while the roughened hydrophilic pHEA layers possessed superhydrophilicity (gamma(tot)(s) similar to 72.1 +/- 0.2 mJ/m(2), Theta similar to 0 degrees). The photoactivity of the composites was presented both in solid/gas (S/G) and solid/liquid (S/L) interfaces. According to the light-emitting diode (LED) light photodegradation tests on ethanol (EtOH) as volatile organic compound (VOC) model-molecules at the S/L interface, the superhydrophobic hybrid layer was photooxidized 88.3% of the initial EtOH (0.36 mM). At S/L interface the photocatalytic efficiency was depended on the polarity of the model pollutant molecules: the photooxidation of hydrophobic SUDAN IV (c(0) = 0.25 mg/mL) dye reached 80%, while in the case of the hydrophilic Methylene Blue dye (c(0) = 0.002 mg/mL) it was only 17.3% after 90 min blue LED light (lambda = 405 nm) illumination.