Preparation,Structure And Properties Of Organic Modified Nano-SiO₂ Superhydrophobic Coatings

For the past few years, superhydrophobic surface, with water contact angle larger than150°, produced by modifying the low surface energy stuff on the surface or by producingmico and nano-structures on the surface, has attracted more and more interest because of theirextensive and attracted potential applications. Up to now, many methods of fabricatingartificial superhydrophobic surfaces have been developed, including template, laser andplasma etching, physical and chemical vapor deposition, sol-gel, electrospinning and others.Unfortunately, these methods have not been used widely due to the limitation of complicatedprocesses and equipments. So it is important and meaningful to search after a kind of simple,low-cost and practical method for preparing super-hydrophobic surface on large area.This paper aims at prepareing nano-SiO₂ superhydrophobic coatings, with micro-nanometer dual rough structure, by sol-gel process,in which monodisperse nano-SiO₂ sol was firstprepared and then modified with low surface energy silicone, includingpolymethylhydrogensiloxane (PMHS, with hydrogen content 0.08% and 0.386%), hydroxylsilicone oil (HTO), hydroxy terminated fluorosilicone oil (HTFO) The silicone-SiO₂ sol wascoated on glass substrates and heat-treated at elevated temperatures for drying and gelation.The preparation conditions, structure and properties of the coatings were investigated bycontact angle measurement, Fourier transfer infrared spectroscopy (FTIR), X-rayphotoelectronic spectrum (XPS), Transmission electron microscope (TEM), Scanning electronmicroscope (SEM), Atomic force microscope (AFM), and et al.The results show that nano-SiO₂ coatings modified by four different kinds of silicone allcan reach superhydrophobic. Compared with the nano-SiO₂ coatings modified by other threekinds of silicone , the nano-SiO₂ coatings modified by polymethylhydrogensiloxane (PMHS,with hydrogen content 0.386%) has the best superhydrophobic properties. The contact angleof the PMHS (with hydrogen content 0.386%)-SiO₂ coatings reaches 173o and rolling angle is0.80 when the coatings is heat-treated at 170℃for 3h. The coatings also have good chemicalsolvent resistance and environment stability. The structure and morphology of the SiO₂ solbefore and after modification and silicone-SiO₂ coatings were studied. The results show that acrosslinked silicone-SiO₂ hybrid material was obtained due to the chemical combinationbetween silicone and SiO₂ surfaces. The excellent superhydrophobic property of the coatingsdue to dual effects of forming an appropriate surface roughness with micrometer-nanometercomposite particles and the low surface energy of silicone. It is known from the experimentresults on the influence of surface structure and roughness of the coatings on the wetting properties, and combined with theoretical analysis that a heterogeneous interface conformingto the Cassie model is formed by silicone modified crosslinked nano-SiO₂ on the surface ofthe coatings.