Study On The Preparation And Application Of Transparent Superhydrophobic Coatings

In recent years, researchers all over the world have paid more attention to the preparation and application of superhydrophobic coatings, which have been fabricated by the bio-mimetic synthesis. As the gradual perfection of nanotechnology, people are tending to discuss the reason and interpretation of superhydrophobic phenomena from the basic mechanism. The superhydrophobic coatings with various functions and application prospects are synthesized, then used in human life and production.Along with the further research on superhydrophobic coatings, higher requirements of the function and application are imposed. The coatings with specific proporties were needed to be prepared according to different applications. For instance, transmittance is one of the most significant parameters for/of superhydrophobic coatings that applied in glass surface and exterior walls of buildings, only if a proper spot of balance can be found between superhydrophobicity and transparency, transparent superhydrophobic coatings that meet people's requirements could be successfully fabricated. In this paper, we devoted to the fabrication of transparent superhydrophobic coatings on glass matrix. Firstly, organic-inorganic hybridization or surface modification of inorganic particles were conducted to increase surface roughness of the matrix, while the size of the nanoparticles were strictly controlled less than 100nm. Then, subsequent modification was carried out to introduce hydrophobic groups on the prepared rough surface, thus transparent superhydophobic coatings with stability and abrasive resistance were well prepared.The main contents and results of the work are as follows:(1) TEOS was used as the silicon source. The PEG/SiO2 organic-inorganic materials were prepared by sol-gel process and organic-inorganic hybridization, which were coated on glass matrix through dipping coating process. Then, rough surface of the glass matrix was fabricated after phase separation. The second step was designed to introduce hydrophobic groups on the prepared coating.1,1,1,3,3,3- Hexamethyldisilazane (HMDS) was used to form strong bond of Si-O-Si consequently, the CH3 groups imparted superhydrophobic property to this coating. Effects of reaction temperature, molecular weight of PEG, mass fraction of PEG and the mixed proportion of PEG/SiO2 to the coatings' transparency and superhydrophobicity were discussed. The optimum condition was determined. The results indicate that the coating can remain superhydophobic after a long period (6 months), the contact angle can reach 168°, transmittance is above 89% in the visible region. All of these suggested that the coating can be applied to the surfaces of glass and other surfaces.(2) Monodispersed SiO2 nanoparticles were prepared via sol-gel process, and then were treated with surface modifier. Modified particles with different diameters were connected to form the micro/nano structure SiO2 nanoparticles. The results shows that the micro/nano structure SiO2 nanoparticles have well-distributed structure which is very samiliar with the surface structure of lotus leaves, and this structure properly coincided with the Cassie Model, therefore it is an important factor in the fabrication of superhydophobic coatings.(3) Dispersed liquid of micro/nano structure SiO2 nanoparticles prepared in the previous chapter were deposited on the surface of glass via dehydration condensation. Then hydrophobic liquid was dipped on the prepared surface of glass to make sure the alkyl chain grafted on the surface, thus superhydrophobic coatings which both contain transparency and superhydrophobicity were well prepared. It can be seen from the contrast experiment that the coatings treated with micro/nano structure SiO2 nanoparticles have exceedingly better hydrophobicity than that treated with simplex SiO2 nanoparticles. In addition, transparency of the coatings was little influenced through control of the particle size. Therefore, it is a key step to realize the change of the coating from hydrophobic to superhydrophobic, which has great directive function for us to prepare and applicate transparent superhydrophobic coatings.