Preparation And Function Of Superhydrophobic Bombyx Mori Fibroin Materials

Superhydrophobic material refers to a material with special wetting properties,that the static contact angle on its surface is greater than 150° and the sliding angle is less than 10°.Such material attracted much attention for its excellent characteristics,including self-cleaning,anti-corrosion,oil-water separation,anti-icing,antibacterial.Bombyx mori fibroin material is a natural environmentally friendly and biodegradable high-molecular polymer.It has been widely used in textile,cosmetics,medicine and other fields.Although silk fabric has smooth feel and good breathability,its highly hydrophilic surface characteristics often cause silk fabrics to be easily contaminated,and it also causes much difficulties in the production of silk fabrics.Therefore,hydrophobic modification of Bombyx mori fibroin material surface is essential to broaden its application.At present,micro/nano topology and low surface energy are the two key factors for obtaining superhydrophobic materials.There have been various modification methods to construct superhydrophobic surfaces.However,report of constructing micro/nano multi-level structures on Bombyx mori fibroin materials to achieve superhydrophobicity is limited.The existing methods are complicated and difficult to produce on large scale.Therefore,in order to achieve superhydrophobicity,simple and effective method constructing micro/nano structures on the surface of Bombyx mori fibroin materials is much needed.In this study,I present two different methods to fabricate superhydrophobic silk fabrics and nanofiber membranes.The self-cleaning and oil-water separation functions of these materials were investigated subsequently.(1)Preparation and characterization of superhydrophobic silk fabricThe preparation of super-hydrophobic silk fabrics by the dip-coating method and following characterization is studied in this section.First,hydrophobic silica(SiO2)nanoparticles were prepared at room temperature.Then,the hydrophobic silica nanoparticles and polydimethylsiloxane(PDMS)were sonicated at different mass ratios to form a uniform coating solution.Finally,the silk fabric was immersed in the coating solution for 20 min.After being taken out,it was dried and cured for 3 hours to obtain a super-hydrophobic silk fabric.SEM observation of surface microstructure shows that porous micro/nano rough structures were formed on the surface of the silk fabric.Through contact angle and sliding angle measurement,it was displayed the obtained silk fabric yield best superhydrophobic performance when the SiO2/PDMS mass ratio was 4:5.The self-cleaning and antibacterial test showed efficient removal of surface pollutants on superhydrophobic fabric.The bacteriostatic rate of E.coli and Staphylococcus aureus is over 90%.The mechanical stability and chemical durability measurement showed that the superhydrophobic silk fabric maintained superhydrophobic after 20 abrasion cycles.There is no significant difference in its superhydrophobic characteristics in weak acidic environment.The results of oil-water separation experiments showed that the oil-water separation efficiency of the super-hydrophobic silk fabric is over 90%,and it performed well for different types of oil-water mixtures.Therefore,the silk fabric showed much potential as selective filtration membranes.(2)Preparation of superhydrophobic silk nanofiber membrane and its oil-water separation performanceComparing with the porous structure of superhydrophobic silk fabric,the fiber membrane prepared by electrospinning method yield higher specific surface area,highly interconnected pore structure and better flexibility.Therefore,it has greater application value for oil-water separation.In this section,I studied the preparation of regenerated silk fibroin nanofiber membrane(ESF)by electrospinning technology,and modified its surface with metal-organic framework.Octadecyl orthophosphate(OPA)grafting and polydimethylsiloxane(PDMS)solution etching were carried out.SEM observation showed that the zeolite imidazolate framework-8(ZIF-8)was stably fixed on the surface of silk fibroin nanofibers.The static contact angle of drafted nanofiber membrane is 153.5°,which is excellent superhydrophobic.The results of oil-water separation experiments showed that the superhydrophobic silk fibroin nanofiber membrane yielded high separation efficiency(>95%)for various oil-water mixtures,and maintains high separation efficiency after 10 cycles.Meanwhile,the superhydrophobic silk fibroin nanofiber membrane is well reusable and chemically stable.It is potential in separation of a variety of common oil/water mixtures,and has broad application prospects.In this study,superhydrophobic silk fabrics and superhydrophobic silk nanofiber membranes were prepared by two different methods.Both showed excellent chemical stability,mechanical durability,and oil-water separation performance.This study expanded the application of Bombyx mori protein materials in the environmental production and broadens the potential of Bombyx mori protein materials.