Preparation And Application Of Pure Natural Protein-based Superhydrophobic Coatings

Inspired by superhydrophobic surfaces in nature,the non-wettability of a superhydrophobic surface facilitates a wide range of applications.Current technologies to prepare a superhydrophobic coating with long-term durability still mainly rely on the use of toxic fluoroalkanes as hydrophobic topping.Although all-natural fatty acids and natural wax are used as fluoroalkanes alternatives,the problems of these materials are the poor hydrophobic effect and the week adhesion force between these substances and a substrate,which result in poor mechanical stability and low long-term durability.Moreover,it is difficult to construct a superhydrophobic coating on a substrate with complex non-flat shapes such as tubes and bags,which severely limits their application in real life to a large extent.In order to solve the above problems,we describe the preparation of all-natural superhydrophobic interface material with mechanical stability and hydrophobic stability in a green,energy-saving and low-cost process,which obtained by introducing carnauba wax on the lysozyme phase transition aggregates layer.Based on the above superhydrophobic surface,this work has developed the applications of the coating in food packaging materials and non-planar materials.The research outline is as follows:(1)The preparation and stability of the superhydrophobic surface.The fast phase transition of lysozyme under a stimulus from cysteine by the thioldisulfide exchange reaction is triggered to prepare the phase-transited lysozyme(PTL)nanofilm and product as the basement.The PTL nanofilm and product could attach on a variety of substrate surfaces due to amyloid-like structures-mediated interfacial adhesion.The superhydrophobic surface with the thickness of 18 ?m was then obtained by introducing carnauba wax on the phase transition layer through spin,spray or dip coating,in which hydrogen bond interactions between the functional groups of the lysozyme(hydroxyl,amino,carboxyl,amide bonds,etc.)and the ester bonds of the wax could enhance the mechanical and superhydrophobic stability.The adhesion force between the carnauba wax and PTL product was 2.8 times higher than that between carnauba wax and glass.The coating would even maintain its superhydrophobicity after bending for 5000 times,mechanical rubbing with sandpaper(grit no.240)for 50 times or dynamic flushing by water.Moreover,the coating could not compromise its superhydrophobic state after immersed in different organic solvent and different pH aqueous solutions and under different temperature environments(30-90?).(2)Multi-functional application of superhydrophobic coating.The resultant superhydrophobic surface noticeably enhances the water repellence of cellulose-based materials(e.g.,paper)and their resistance to mold without compromising their mechanical stability and usability.In addition to pure water,the superhydrophobic coating further resists the adhesion of a wide range of food residues(e.g.,milk,yogurt,honey and beverages as well as other edible liquids)and biofluids(e.g.,blood and urine).The coating has good biocompatibility including the non-toxic to 3T3 cells and excellent blood compatibility,and decreases the adhesion of platelet and protein on corresponding surfaces.The competitive advantage of this method is further highlighted by showing its capability to easily coat non-flat substrates(e.g.,the interior spaces of tubes and 3D-printed resin).Therefore,the method and corresponding materials in this study are highly useful for developing recyclable packaging materials and biocompatible blood-contacting materials.