Preparation And Property Study Of Several Bionic Super-wetting Materials

As a new generation of bionic functional materials,super-wetting materials with high contact angle and low adhesion towards liquid droplets have drawn extensive research interest.A large number of research results have indicated that the superior performances of super-wetting materials are primarily determined by their surface structures and chemical components.However,conventional superhydrophobic materials fail miserably at meeting demand for practical applications,due to their weak mechanical strength,high cost,complicated fabrication process and other problems.Therefore,developing novel,high-performance,durable and low-cost super-wetting materials are always the hotspots.In the future,scientists will focus much on exploring new-type coating materials,regulating the wetting of special materials,and directing new application fields.To this end,this paper elaborates the mechanisms and features of super-wetting materials at first.Next,the research status,merit and demerit of super-wetting materials are systematically summarized.On these bases,we primarily study several properties of bionic super-wetting materials,and demonstrate their preparation methods and research means in detail.1)Taking citric acid monohydrate（CAM）as pore-forming agent,ultrathin porous PVDF membranes are successfully fabricated by a combined method of recrystallization and in-situ elimination for the first time.After investigating the effects of pore-forming agent on the porosity of membranes,the optimum recipe of 0.8 mmol CAM in 10 mL 6%PVDF solution is prescribed.Meanwhile,SEM、XPS、FTIR and contact angle meter are conducted to analyze the surface microtopography,chemical components and wettability of prepared membranes,as well as the pore-forming mechanism.The results show that the obtained PVDF membranes possess porous network structures with thickness of⁵μm and apparent pore size of<500nm,and display superoleophilic/under-oil superhydrophobic properties.Taking use of the porosity and super-wettability of the membranes,both immiscible water/oil mixtures and surfactant-stabilized water-in-oil nanoemulsions are efficiently separated.Dynamic light scattering（DLS）is thus used to investigate the separation effects,and the results show that the separation speed is up to 318 L m^-2 h^-1 and separation efficiency is as high as 99.81%.2)Hierarchical flower-like TiO₂ particles are prepared by a glycerolysis-assisted co-solvothermal method.After calcination and perfluorinated silane treatments,multifunctional superamphiphobic FOTS-TiO₂ powder and coatings are obtained.The structures,crystalline types and chemical components of the particles obtained before and after treatments are characterized using SEM,TEM,XRD and XPS.It is found that the calcination and modification treatments not only retains their flower-like structures,but also lower their surface energy.This superamphiphobic powder show strong repellency towards water,cooking oils,as well as most organic solvents（e.g.,n-hexadecath,1,2-dichloroethane,cyclohexane,and n-decane）.With a model,the superiority of lower-like quasi-spherical particles in superoleophobicity is demonstrated in term of structural features.With the aid of double-sided tape or spray adhesive,the superamphiphobic powder can be firmly bonded onto various substrates for robust superamphiphobic coatings.In addition,the excellent mechanical durability,self-cleaning,anti-fouling and anti-icing properties of the coating materials are further investigated.3)We report the design and preparation of different“superhydrophobic sands”for the first time,by structuring desert sand with the inorganic SiO₂,metal Ag or Cu materials,and then modifying them with the low-surface-energy chemicals of perfluorinated silane or n-octadecanethiol.To verify the special characteristics of the surface structures and chemical components of the resultant products,SEM,EDXS,XPS and FTIR are performed on various products,and the results are analyzed in detail.The results show that the sand grains coated by SiO₂ and modified with perfluorinated silane display the best water repellence with water contact angle of>150°and rolling angle of<10°.Aiming at the desert water storage and transportation,the heat-resistant,water-holding and water-flow-dragging capacities of this superhydrophobic sand are tested.It is primarily confirmed that 20 cm thickness of superhydrophobic sand layer can sustains 25 cm height of water column.Very significantly,such superhydrophobic sand exhibits extremely high thermal stability up to 400°C when used for water storage.In addition to reliable water storage,such superhydrophobic sand also demonstrates a great anti-flow-dragging effect during water transportation,whereby a water droplet can smoothly and quickly roll down a simulated sand channel（13 cm length）within0.3 s（⁰.45 m/s）.All of these manifestations imply the significant potential of such“superhydrophobic sand”in its application to desert water storage and transportation.In sum,based on different materials（i.e.,polymer,inorganic particle,and desert sand）,we try to regulate their surface structures and wettability,and primarily investigate several important properties,including emulsion separation,superoleophobicity,desert water storage and transportation,and others.