Study On Fabrication And Performance Of Zwitterionic Polymer Antifouling Materials

With gradual improvement of people's awareness of environmental protection,marine anti-fouling technology is now developing in an environmentally friendly direction.Zwitterionic polymers have no biological toxicity,but can inhibit the attachment of fouling organisms through electrostatic hydration,showing a broad development prospect in the field of marine anti-fouling.However,the modification methods of zwitterionic polymers on the surface of materials are quite complex,and their mechanical properties and durability in the real marine environment are not good enough.These two problems greatly limit the practical application of zwitterionic polymers.This thesis mainly addressed the problem of complex modification methods of zwitterionic polymers on the surface of materials.Herein,poly sulfobetaine methacrylate(PSBMA),one of the most typical zwitterionic polymers,was selected as representative,aluminum,B30 copper alloy and 316L stainless steel,these three commonly used metal materials,were used as substrates,three surface modification methods of zwitterionic polymers as well as their antifouling performance and mechanism were studied.(1)Anodic aluminum oxide(AAO)formed by anodization of aluminum has honeycomb-like nanopores,which is an ideal template for preparing one-dimensional nanomaterials.In this thesis,aluminum was used as the substrate and anodized in oxalic acid solution to obtain AAO with highly ordered nanopores.Then,a mixed solution of acrylic acid and sulfobetaine methacrylate(SBMA)was injected into the nanopores and copolymerized to obtain a zwitterionic nanofiber film.Owing to the highly ordered nanopores of AAO,the zwitterionic nanofiber film has a uniform fibrous nanostructure,and the diameter of the single nanofiber is about 65 nm.Additionally,due to the presence of PSBMA,the zwitterionic nanofiber film is super-hydrophilic,and the static water contact angle on its surface is 7.6°.The fibrous nanostructure and super-hydrophilic properties of the zwitterionic nanofiber film can work synergistically to exert a better antifouling effect.The results of fouling microorganism adhesion test showed that the zwitterionic nanofiber film has an inhibition rate of over 99%again st Pseudomonas aeruginosa(aerobic bacterium),Desulfovibrio vulgaris(anaerobic bacterium),and Chaetoceros muelleri(diatom)within 30 minutes,showing excellent antifouling performance.The results of adhesion test of extracellular polymer substances(EPS)showed that the zwitterionic nanofiber film can effectively inhibit the adhesion of EPS and maintain the original surface micromorphology,thus achieving the effect of inhibiting the adhesion of fouling microorganisms.(2)Polydopamine(PDA)formed by oxidative polymerization of dopamine under alkaline conditions can be deposited on the surfaces of almost all organic or inorganic materials.Moreover,PDA contains a large amount of catechol and amino groups,which is an ideal platform for secondary functional modification.In this thesis,PDA was used as the intermediate layer,and a zwitterionic polymer coating was successfully prepared on the surface of B30 copper alloy by a two-step deposition method.Due to the presence of PDA,the zwitterionic polymer coating is brown.Because of the two-step deposition method,the zwitterionic polymer coating has a double-layer microstructure,the lower layer is a spherical PDA,and the upper layer is an irregular sheet of PSBMA.The hydrophilicity of B30 copper alloy is greatly improved after modification of the zwitterionic polymer coating,and the static water contact angle on its surface is decreased from 61.7° to 8.3°,reaching a super-hydrophilic state.The results of fouling microorganism adhesion test showed that the inhibition rates of the zwitterionic polymer coating against Pseudomonas aeruginosa(gram-negative bacterium)and Bacillus subtilis(gram-positive bacterium)were 98.1%and 98.5%within 30 minutes,and 98.9%and 99.5%within 24 hours,indicating that the zwitterionic polymer coating has excellent antifouling properties(3)In this thesis,the method of two-step deposition with PDA as the intermediate layer was improved,and a zwitterionic polymer coating was successfully prepared on the surface of 316L stainless steel by "one-step method".This method uses semiquinone radicals generated by the oxidation of dopamine to initiate the polymerization of SBMA,so that PDA and PSBMA can simultaneously generated and deposited on the material surface,thus simplifying the preparation process of the zwitterionic polymer coating.Moreover,this method also uses CuSO4 and H2O2 as oxidants to accelerate the generation of the semiquinone radicals,which greatly shortens the reaction time to 30 minutes.The zwitterionic polymer coating prepared by the "one-step method" has a large amount of densely distributed nanoparticles with a diameter of about 40 nm.The hydrophilicity of 316L stainless steel is greatly improved after modification of the zwitterionic polymer coating,and the static water contact angle is decreased from 49.7° to 7.3°,reaching a super-hydrophilic state.The results of organic adsorption test showed that the zwitterionic polymer coating can effectively inhibit the non-specific adsorption of proteins and polysaccharides,and the results of fouling microorganism adhesion test showed that the zwitterionic polymer coating has an inhibition rate of over 99%against Pseudomonas aeruginosa(gram-negative bacterium)and Bacillus subtilis(gram-negative bacterium)within 24 hours,indicating that the zwitterionic polymer coating prepared by the "one-step method" also has excellent antifouling properties.