Preparation And Properties Of Chitooligosaccharides-based Coatings

Marine biofouling will accelerate the corrosion of ship bottom and greatly reduce the service life of underwater equipment.According to incomplete statistics,marine biofouling alone in the world will cause economic losses of tens of billions of dollars to various underwater engineering facilities and naval equipment every year.Therefore,it is of great significance to seek efficient,long-term and environmentally friendly marine antifouling methods for us to develop ocean resources.In this paper,chitosan oligosaccharides were prepared by degradation of chitosan and modified to prepare antifouling coatings.The structure of the coatings was characterized by FT-IR.The wettability of the coatings was characterized by static contact angle test.Marine defense of the coatings was studied by seawater immersion test,seaweed immersion test,bacteriostasis test and protein adsorption test.Chitooligosaccharides were prepared by the combination of acetic acid,lysozyme and ultrasonic degradation.The results showed that the molecular structure of chitooligosaccharides was the same as that of chitosan,but the chain length and conformation changed.As the concentration of acetic acid increases and the sonication time increases,the degree of degradation increases.Chitooligosaccharides had no toxicity to algae,and had better bacteriostatic effect and solubility than chitosan.Two copolymer coatings,COS-AA and COS-HEAA,were prepared by the reaction of hydroxyl groups on the chitosan oligosaccharide molecular chain with epoxy group of glycidyl methacrylate,and the reaction of double bonds on the other end of glycidyl methacrylate with acrylic acid and N-hydroxyethyl acrylamide,respectively.The static contact angle of the coating is between 40oand 50o,and the weight loss is about 40% after 20 days immersion in seawater.The weight loss in algae is higher than that in seawater,and it also has certain bacteriostatic and antiprotein adsorption effects.The COS-AA/HEAA-SLA coatings were prepared by crosslinking the graft copolymer COS-AA/HEAA with sodium alginate through calcium ions,and copper ions were introduced into the coatings.The coatings are hydrophilic and can achieve sustained release of copper ions,which can effectively kill algae and bacteria in the surrounding environment and deactivate the proteins adhering to the surface.The release of copper ions and the hydrolysis of the coatings make the coatings lose weight when immersed in seawater.The weight loss rate of the coatings is less than 30%.Moreover,the cross-linked coatings have better sustained release effect and lower weight than the uncrossed coatings.The graft copolymer COS-AA/HEAA was blended with polyvinyl alcohol,and a small amount of glycerol was introduced to prepare COS-AA/HEAA-PVA coating.The static contact angle of the coating decreases with time,and finally shows good hydrophilicity.The tensile strength of the coating is more than 7 times higher than that of the grafted copolymer coating.The weight loss rate of the coating in seawater is lower,and the weight loss rate of the coating with volume ratio of 80:20 is lower than that of other proportions.The anti-fouling performance of COS-AA-PVA coatings increases with the increase of PVA content in the system,but the proportion of COS-HEAA-PVA coatings has little effect on the performance.