Research And Preparation Of Superhydrophobic Silica Thin Films By Emulsion Method

We talked about and concluded the superhydrophobic theories and the new techniques in preparation superhydrophobic surfaces out and in recently, and introduced the main theories, teniques and application foreground. We have discussed the disadvantages existed in the superhydrophobic coating preparation and gave some advices of development in the future, particularly presented the peculiarity, main theories and influence factors in emulsion method. At last we talked about the theories for preparation superhydrophobic thin films by emulsion method.In this work, a new, simple and convenient superhydrophobic surface preparation method was reported in this article, and obtained superhydrophobic films on the glass substrates. Superhydrophobic porous silica films with honeycomb like structure was fabricated assistant by the discontinuous droplets distributing in the O/W emulsion system. The result indicated that the porous structure was obtained during the films drying progress and conserved during the annealing progress. The films changed from superhydrophilic to superhydrophobic after modified by the octyltrimethoxysilane via phase deposition, the WCA was up to 156.3°. And then the superhydrophbic films with hierarchical structure preparation techniques were studied by combining the sol-gel method and the template method. Firstly, silica films with hierarchical structures were prepared by employing the polytetrafluoroethylene (PTFE) sol particles emulsion as template and the silica hydrosol as films precursor material. The films changed from superhydrophilic to superhydrophobic after modified by trimethylchlorosilane, the WCA is 163.5°and the roll-off angel is smaller than 10°. The films showed excellent superhydrophobic self-cleaning properties. At last, silica films with micro- and nano-region alternating structures were obtained by employing polymethylmethacrylate microsphere prepared by emulsion method as template and the silica hydrosol as films precursor material. The films had WCA about 150.7°and roll-off angel greater than 10°after modified by hydrophobic reagent. We designed and invited the phase deposition instrument ourselves, and investigated the phase deposition process in-deep.The sol particles were characterized by the transmission electron microscopy and the particles size distribution was analyzed by the laser fineness analyzer. The films surface structures were studied by the AJ-Ⅲa atomic force microscope and the scanning electron microscopy (SEM). The films were modified before and after were characterized by Fourier Transform Infrared Spectrometry (FTIR), and then the bond style between hydrophobic molecules and the films were discussed.The conclusions are as followed:(1) The emulsion method, combination of sol-gel method and the template method are new techniques for superhydrophobic or rough films preparation. The buildup of emulsifier, the HLB value, concentration of TEOS and the temperature all have strongly influences on the stability of the emulsion systerm.(2) The microscale roughness is the most important key factors to the superhydrophobic properties, while the nanoscale roughness to the small roll-off angel. The enwrapping of air is attributed to the cooperation of the micro and nanostructures or called hierarchical structure; this debased the surface energy and enlarged the WCA of the films.(3) The traditional hydrophobic treatment process did not mature enough, the property of the most modified films can not stand too long as the hydrophobic reagent molecules existing behavior is physical absorption, and there is no chemical bond.(4) The preparation processes have important influence on the mechanical intensity. The porous films prepared by O/W emulsion method and the films prepared by employing PTFE sol particles emulsion as template and the silica hydrosol have high mechanical intensity while the polymethylmethacrylate microsphere as template one has poor of that.