Study On The Construction And Properties Of Hydrophobic Surfaces Based On Anchoring Effect Of Polysilazane

Hydrophobic surfaces,especially superhydrophobic surfaces,have been proved to possess many excellent properties such as self-cleaning/easy-cleaning,drag reduction,antifouling,anti-bioadhesion,anti-corrosion and so on,thus showing broad application prospect in the fields of building exterior walls,shipbuilding industry,medical devices,fluid transportation,kitchen and bathroom ware,and material protection.In recent years,the construction and application of hydrophobic/superhydrophobic surfaces have became one of the most important research directions in the field of functional surfaces.From the observation and studies on many biological hydrophobic/superhydrophobic surfaces in nature,it has been found that the chemical composition and rough structures of the solid surfaces are two important factors for their hydrophobicity.The low-surface-energy substances or materials are usually necessary for constructing hydrophobic surfaces,and the micro-/nanometer rough structure rough on the solid surfaces can further enhance their hydrophobicity,so as to achieve superhydrophobic surfaces.Based on this understanding,various methods have been developed for constructing hydrophobic/superhydrophobic surfaces,and many functional surfaces with excellent hydrophobicity/superhydrophobicity have been fabricated.However,in the construction of hydrophobic/superhydrophobic surfaces there is a long-standing basic and common problem,which is that poor adhesion of the low-surface-energy materials used for surface modification to the substrate inevitably makes the prepared hydrophobic/superhydrophobic surfaces exhibit the poor stability and durability,and then cannot meet many practical application requirements.To solve this problem,we put forward a research thought of constructing the polysilazane-based functional surfaces with hydrophobicity/superhydrophobicity by using the reactive polysilazane with excellent anchoring effect and physical and mechanical properties as an anchor material,and using low-surface-energy substances and modified SiO₂ nanoparticles as functional components for surface modification.The structure-activity relationship of the constructed polysilazane-based hydrophobic/superhydrophobic functional surfaces is established by investigating and comparatively analyzing their chemical compositions,morphologies,wettability and durability,self-cleaning/easy-cleaning properties and the anti-bioadhesion properties.Furthermore,the anchoring effect of polysilazane was investigated by in-depth study on the interface interaction between the polysilazane-based coating and the substrate,thus laying a theoretical and practical foundation for the construction of stable and durable functional surfaces with hydrophobicity/superhydrophobicity.The main contents and results of this work are described follows.1.Two different types of low-surface-energy polymer,fluorinated acrylic copolymer bearing hydroxyl group（PDFHE）and isocyanate-terminated polydimethylsiloxane（PDMS）oligomers（PDMS-NCO）,were designed and synthesized based on free radical copolymerizationandpolyadditionreaction,respectively.Aseriesof organopolysilazane（OPSZ）/PDFHE coatings and OPSZ/PDMS coatings with various proportions were fabricated via dipping and heat treatments on three different substrates,including glass slide（Glass）,304 stainless steel（SS）and polyethylene terephthalate film（PET）,by using OPSZ as the main resin and PDFHE and PDMS-NCO as the low-surface-energy components,respectively;and their surface physical and chemical characteristics were investigated.The results indicate that the adhesion between the OPSZ/PDFHE coatings or the OPSZ/PDMS coatings and substrate both reach Grade 0,which shows excellent adhesion to the substrate;the hardness of the OPSZ/PDFHE coatings and the OPSZ/PDMS coatings could reach 4H and H,respectively;with increasing the amount of low-surface-energy components of coatings,the roughness of the prepared OPSZ/PDFHE coatings and OPSZ/PDMS coatings increased,respectively,while the water contact angle（WCA）values of both OPSZ/PDFHE coatings and OPSZ/PDMS coatings do not increase significantly and have nothing to do with the types of substrates,the WCA values of above two types coatings are in the range from 107°to 110°and from 105°to 109°,respectively;besides,the transmittance at 550 nm(T₅₅₀)of the prepared OPSZ/PDFHE coatings and OPSZ/PDMS coatings using Glass as substrate were both closed to the pristine Glass,showing great transparency;the prepared OPSZ/PDFHE coatings and OPSZ/PDMS coatings also exhibit excellent easy-cleaning properties.2.Anti-bacterial adhesion behaviors of the prepared OPSZ/PDFHE coatings and OPSZ/PDMS coatings were measured by a bacterial adhesion experiment via using Gram-negative bacterium Escherichia coli and Gram-positive bacterium Staphylococcus aureus as test bacteria.The results indicate that F-OPSZ-6@Glass and Si-OPSZ-6@Glass containing PDFHE and PDMS-NCO,respectively,possess anti-bacterial adhesion properties by comparison with pristine Glass,the bacteria adhered to them are much less than the pristine Glass;in addition,the bacteria adhered to the Si-OPSZ-6@Glass are much less than the F-OPSZ-6@Glass,showing better anti-bacterial adhesion properties.3.A series of multilayer coatings with various OPSZ/F-SiO₂ bilayers（OPSZ/F-SiO₂）_n（n=0.5,1,1.5,?,5）were constructed on glass slide substrates using OPSZ and fluorinated silica nanoparticles（F-SiO₂ NPs）by alternately spraying layer-by-layer.The chemical compositions,microstructure,wettability,transmittance,self-cleaning properties and mechanical and chemical durability were characterized and analyzed.With the increase in the number of OPSZ/F-SiO₂ bilayers,the roughness and WCA values of the prepared multilayer coatings（OPSZ/F-SiO₂）_n（n=0.5,1,1.5,?,5）show a fluctuating but overall increasing trend.The multilayer coating containing five OPSZ/F-SiO₂ bilayers,（OPSZ/F-SiO₂）₅,was translucent and the transmittance at 550 nm(T₅₅₀)of the multilayer coating was 39.4%.The coating exhibited hierarchical micro/nanostructures,and its WCA was 158.3°and slide angle（SA）was 3°,the adhesive force of a water droplet on the coating surface was just about 13μN,showing excellent superhydrophobicity.In addition,the surface of the multilayer coating（OPSZ/F-SiO₂）₅ also exhibited good self-cleaning properties and excellent mechanical durability.In particular,the WCA of the coatings could still reach 151.2°even after 40 abrasion cycles with sandpaper.4.A series of multilayer coatings with various OPSZ/Si-SiO₂ bilayers（OPSZ/Si-SiO₂）_n@Glass（n=0.5,1,2,?,6）were constructed on glass slide substrates using OPSZ and PDMS-modified silica nanoparticles（Si-SiO₂ NPs）by alternately spraying layer-by-layer.The chemical compositions,microstructure,wettability,transmittance,and mechanical and chemical durability were characterized and analyzed.With the increase in the number of OPSZ/Si-SiO₂ bilayers,the roughness and WCA values of the prepared multilayer coatings（OPSZ/Si-SiO₂）_n（n=1,2,?,6）show a tendency to increase.The multilayer coating containing six OPSZ/Si-SiO₂ bilayers,（OPSZ/Si-SiO₂）₆@Glass was translucent and the transmittance at 550 nm(T₅₅₀)of the multilayer coating was 43.1%.The coating exhibited hierarchical micro/nanostructures,and its WCA was 155.7°and slide angle（SA）was 6°,showing excellent superhydrophobicity.In addition,the surface of the multilayer coating（OPSZ/Si-SiO₂）₆ also exhibited excellent mechanical durability.In particular,the WCA of the coatings could still reach 150°even after 46 abrasion cycles with sandpaper.Besides,all the WCA values of the（OPSZ/Si-SiO₂）₆ coatings constructed on other different substrate,such as stainless steel,PET nonwovens and copper foam,were above 150°,showing good Substrate universality to substrates.5.Ultra-thin OPSZ coantings and thick OPSZ coatings were constructed on SS substrates using OPSZ with propyl triethoxysilane by spinning and dipping,respectively.The chemical compositions of the Ultra-thin OPSZ coantings,the thick OPSZ coatings and the pristine SS were characterized and analyzed.The results indicate that the oxides and hydroxides of Fe and Cr existed on the surface of SS could react with OPSZ to form covalent bonds,Cr-O-Si and Fe-O-Si,at the interface between OPSZ coatings and SS substrate.The OPSZ molecules can be firmly anchored to the surfaces of SS substrate,which due to the formation of these covalent bonds,thereby endowing OPSZ coating with an excellent anchoring effect to anchor on the surfaces of SS substrate.