Preparation And Properties Of Transparent Superhydrophobic Functional Coating Suitable For Glass Substrate

In the 1970s,German plant taxonomist William Barth·lott first discovered the lotus leaf effect.The lotus leaf effect is mainly due to the presence of a layer of natural waxy superhydrophobic film on the surface of the lotus leaf,which makes the water droplets collect on the lotus leaf.When the stream flows down,it can take away the dirt on the surface of the lotus leaf.This is the lotus leaf effect.According to this,Professor William Barthlott invented the self-cleaning technology.Since then,many researchers have been interested in the study of biomimetic superhydrophobic materials.With the deepening research of superhydrophobic materials,superhydrophobicity are defined as a surface phenomenon which water droplets are spherical on the surface with a contact angle greater than 150°and rolling angle less than 10°.Such superhydrophobic properties are mainly determined by surface structure and chemical properties.At present,the way to prepare superhydrophobic surfaces is usually to construct the surface roughness of materials and then modifying it with low surface energy substances.Superhydrophobic materials can be widely used in various fields.With the rapid development of new energy,the application of solar cell photoelectric conversion technology has expanded,and the corresponding transparent superhydrophobic materials have been greatly developed.It can be applied to the self-cleaning of photovoltaic panels.Not only that,it also can be further used in architectural glass curtain walls,automotive glass,optical lenses and other fields,Thats all due to its excellent self-cleaning performance.As we all know,the surface roughness and transparency of transparent superhydrophobic materials are competing properties.Increasing the surface roughness can effectively improve the hydrophobicity of the surface,but at the same time it will also increase the scattering of light,which will reduce the transparency of the surface.Find the best balance between the two performance trade-offs.However,the development of Transparent superhydrophobic materials still has many difficult problems such as complicated preparation process,high cost,and poor durability.The above two issues have great research value and far-reaching significance,and many scientific researchers are constantly exploring and researching.In this paper,firstly,the basic theoretical model of superhydrophobicity is systematically expounded;secondly,the construction principles of transparency and stability in the preparation process of transparent superhydrophobic coatings are introduced in detail;and the common methods for preparing transparent superhydrophobic coatings in recent years are reviewed.On this basis,our research work on transparent superhydrophobic thin films is mainly as follows:（1）SiO₂ sol-gel was prepared by one-step alkali-catalyzed method,and the size of SiO₂nanoparticles was less than 50 nm.The hydrophobic silicon dioxide nanoparticles were prepared by hydrothermal modification with Hexamethyl disilylamine（HMDS）.Polysiloxane（PMS）Sol was prepared by acid-base two-step method with methyl triethoxysilane（MTES）,and the transmittance change of PMS Sol induced by the change of NH₃·H₂O was investigated.The cross-linked grid was filled with hydrophobic SiO₂nano-particles and PMS Sol to improve the transmittance.（2）In order to solve the problem of film stability,we prepared precursor solution with silane coupling agent（KH-560）,and spin-coated the precursor on glass substrate and then treated at high temperature to obtain anti-reflective superhydrophilic coating.On this superhydrophilic coating,we carried out surface hydrothermal chemical modification,and got coatings with different effects.Based on this,we changed our thinking to take KH-560 as the intermediate connecting layer,use hydroxyl group generated by epoxy ring-opening reaction of KH-560 to realize chemical bonding with SiO₂,and then use high-temperature annealing to make coupling agent-OCH₃form chemical bond with-OH on glass surface,Indirectly achieve strong bonding between SiO₂and glass substrate,and use simple evaporation form to carry out surface modification with 1H,1H,2H,2H-Perfluorodecyltrimethoxysilane（FAS-17）to obtain superhydrophobic performance,in order to maintain the transmittance,the modifier A is introduced to build a special micro-nano structure on the surface of the film to improve the surface transmittance.we have made different pre-activation of the substrate,the aim of which is to make the surface of the glass more rich in hydroxyl and to make the silane coupling agent further combine with the surface of the glass substrate.We adopt three methods of chemical alkali activation,UV treatment activation and ALD-assisted deposition oxide activation to get different results of super-hydrophobic films.