Fabrication Of Superhydrophobic/Superhydrophilic Surfaces From Silica Nanoparticals Functionalized With Organic Amine

Materials with special wettability, such as superhydrophobic/hydrophilic materials ect, have attractedmuch attention in recent years because of its exceptional properties such as self-cleaning, anti-corrosion,anti-fogging, anti-reflective properties. Silica nanoparticles have become one of the main materials tofabricate superhydrobic or superhydrophlic surfaces due to its nontoxicity, good stability and goodmonodispersion, etc. Therefore the synthesis of monodisperse silica particals with uniform size is crucial tobuild coatings with special wettability. The main sections of this paper are as follows.1. Based on St ber method, the solid/mesoporous silica particles, of which the size covers a wide rangefrom several nanometers to about500nm, are synthesized using small organic amines (SOAs) as catalysts.Also, the size of silica particles can be tuned via selecting various kinds of SOA. The size of silica particlesare considerably reduced taking into the encapsulation of silica oligomers which are surrounded by SOAsand therir protonated products during the process of TEOS hydrolysis and subsequent condensation.Furthermore, the increase in the amount and length of alckyl chain bonded with N atom accounts for thelarge steric barrier and therefore leads to the reducing size of silica particles.2. Collodial silica particles are hydrophobized by co-condensation of tetraethoxy silane andhexamethylsilazane (HMDS). Effects of the concentration of TEOS, ammonia, HMDS on the particle sizesand morphology of SiO2were investigated by DLS, SEM and TEM. The contact angle of water on thecoating can be as high as162°with the sliding angle less than5°. The process is simple and versatileallowing for without additional hydrophobic treatment.3. A transparent superhydrophilic SiO2coating was fabricated through dip-coating mesoporous SiO2nanoparticles on common glass slide. The maximum transmittance of the coated glass was up to97.3%,the contact angle of water is less than5°. Furthermore, the coating exibits excellent anti-fogging property.After treatment with fluoroalkylsilane (FAS), the coating shows superhydrophobicity and water contactangle on the coating>150°.4. A transparent superhydrophobic surface was fabricated through layer-by-layer assembly of silicananoparticles and sacrificial polystyrene nanoparticles, followed by hydrophobic treatment with fluoroalkylsilane (FAS). The superhydrophobic coating with water contact angle166°was obtained.Morphology of obtained coatings was examined by SEM and chemical structure together with constitutionwas analyzed by using FT-IR and TGA.