Function-guided Synthesis And Properties Of Special Wetting Surface

All kinds of materials with special wetting properties surface have aroused extensive concerns in recent years. They have been widely applied in fields of surface self-cleaning, oil and water separation, oil adsorption, energy storage batteries and sensors. The special wettablity properties of surface include superhydrophobicity, superhydrophilicity, superoleophilicity and superoleophobicity. A lot of new materials with advanced functions can be obtained through a multiple combination of these four special wetting properties. In this paper we use simple methods to prepare membranes and coatings with special wettability.The main contents are as follows:Firstly, we fabricated a super-hydrophilic and oleophobic poly?acrylic acid?-grafed PVDF membrane by phase inversion method, and the saturated sodium chloride solution was used as coagulation bath, by adding polyvinylprrolidone?PVP? to improve the separation efficiency during the oil and water separation process.The result showed that: the PVDF-g-PAA membrane could be used to separate not only simple oil and water mixture, but also the oil-water emulsion, which was difficult to separated before. The PVP in the membrane acted as porogen to produce holes which can notably improve flux and separation efficiency during separation process.When the content of PVP was 5 wt%, the separation efficiency of oil-water mixture achieves above 98%, and that of oil-water emulsion still reaches 90% after repeated several times, also the flux may be maintained at 408 L · m-2 · h-1 or more. The membrane can resist oil pollution and has better mechanical strength, and can be used repeatedly.Secondly, we obtained a stable, transparent, super-hydrophobic glass. The super-hydrophobic coating dispersion was got by mixing 30 nm SiO₂ with 200 nm SiO₂ in ethonal, and then hexadecyltrimethoxysiliane was used to modify the SiO₂ nanoparticle in order to prepare superhydrophobic coating. Finally, super-hydrophobic glass was obtained by dipping method or spraying. The transparency of this glass can be adjusted by changing the coating concentration.The result showed that when the mass ratio of 30 nm SiO₂ and 200 nm SiO₂ is 5:1, the coating showed superhydrophobicity with suitable micro-nano structure, the contact angle is more then 150° and the roll-off angle is less then 5°. The coating can be coated on all kinds of substrates without any pretreatment. By using the method of adhesive to improve adhesion between the super hydrophobic layer and the glass substrate, stable super hydrophobic coating were obtained.The glass still have superhydrophobic performance after water washing and finger scraping.Also the coating coated on other substrate,like fliter paper,cotton,non-woven fabric,and etc.Thirdly, we prepared silicon dioxide water dispersions by mixing 30 nm SiO₂ with 200 nm SiO₂, using the poly dimethyl diallyl ammonium chloride and sodium perfluorooctanoate as the low surface modifier, then sprayed the dispersion on the stainless steel mesh and obtained stainless steel mesh with special wetting properties.The result showed that when there is only 30 nm SiO₂ in the dispersion, the coating showed superhydrophilicity and oleophobicity; with the increase of 200 nm SiO₂, the coating exhibited hydrophobicity and superolephobicity; when the ratio reached 1:1, the coating showed superamphiphobicity, the water contact angle is 153 o, the oil contace angle is 158°; with the 200 nm SiO₂ further increase, the coating become hydrophobicity and olephobicity again. When the coating is make up only by 200 nm SiO₂, it was hydrophobicity and oleophobicity coating with the water contact angle 134° and oil contact angle 104°.