| There are many methods for preparing hydrophobic surfaces,but most of the preparation methods are complicated and cumbersome,and are not suitable for industrial mass production.And the most critical problem is that most hydrophobic surfaces will use silane coupling agents containing long fluorocarbon chains for modification,introducing low surface energy chemical structures to achieve hydrophobic or even superhydrophobic features.However,the silane coupling agent which contains long fluorocarbon chains is very difficult to degrade in nature,which can easily accumulate in the biological chain and is harmful to the human body.It is also expensive,which is extremely disadvantageous for expanding production.Compared with compounds containing long fluorocarbon chains,compounds with short fluorocarbon chains can be easily decomposed in the environment with low toxicity.Based on the fact that the silane coupling agent containing long fluorocarbon chains is expensive and not environmentally friendly,in the second part of this thesis,six kinds of fluoride-containing silane coupling agents containing short fluorocarbon chains were successfully synthesized via anion ring-opening polymerization and hydrosilylation,and using cheaper trifluoropropylmethylcyclotrisiloxane,dimethylchlorosilane,methyldichlorosilane and vinyltrimethoxysilane(VTMS)as reactants.Three fluoride-free silane coupling agents were also synthesized as comparison.The structure and molecular weight of the product were characterized by means of 1H-NMR,FT-IR and GPC.The structure of the oligmeric product was confirmed and the molecular weight distribution was narrow.In the third part of this thesis,hydrophobic coating substrate was constructed by sol-gel method.Firstly,nano-silica sols with different particle sizes were prepared by sol-gel method by controlling the amount of ammonia added.The morphology,particle size and size distribution of nano-silica sols were analyzed.The mechanism of preparation of nano-silica sols by sol-gel method was also discussed.Secondly,six nano-silica sols with smaller particle size were selected.KH550 was added into sols and sols were acidified by acetic acid.Then sols were spin-coated on the surface of the glass to form a coating substrate,so that the surface of the glass formed a micro-nano roughness structure.The hydrophobic coating was obtained after the modification of heptafluorodecyltrimethoxysilane.The result showed that the hydrophobic coating prepared was the most ideal when the particle size of the silica sol was 58 nm.The modified coating showed the contact angle about 151.0°,revealing superhydrophobicity,which had suitable surface morphology with obvious surface roughness,while visible light transmittance of the coating reached to 85.5%.In the fourth part of this thesis,a silica sol with the particle size of 58 nm was selected and spin-coated on the surface of the glass to form a coating substrate,and then the surface modification was carried out by using the silane coupling agents synthesized in the second part.The effects of the structure of silane coupling agents on the hydrophobic properties,adhesion,hardness and transmittance of the coatings were investigated.The results showed that for the same type fluoride-containing silane coupling agents,the contact angle increased with the fluorine content in the agents.For the fluoride-containing silane coupling agents which had the similar molecular weight and fluorine content,the hydrophobicity of the coating modified by linear type was better than that modified by branched type.Among the fluoride-containing silane coupling agents in this work,the coating modified by the branched type with the degree of polymerization of 9(DF3)showed the biggest contact angle,about 141.6°,The adhesion level of the hydrophobic coatings in all cases reached to level 1 and the hardness reached to H,while the visible light transmittance was higher than 82.9%.The hydrophobic coating also had good self-cleaning property. |
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