Preparation And Properties Of Degradable Hyperbranched Zwitterionic Antifouling Polymers

The adhesion,growth and accumulation of marine microorganisms,animals and plants on the surface of submerged facilities have serious impacts on marine industries.Zwitterionic polymers have attracted increasing attention due to their excellent fouling resistance ability and eco-friendliness.Yet,the high hydrophilicity and polarity make them difficult to be compatible with other nonpolar polymers,swell easily in seawater,and have poor mechanical properties.Meanwhile,traditional zwitterionic polymers are not degradable,and their surface could be covered by inorganic substances or dead bacteria in the complex marine environment,making their antifouling properties ineffective.In this thesis,aiming to solve the above problems,we have designed and prepared two degradable hyperbranched zwitterionic antifouling polymers,and investigated the relationship between their structure and performance.The main results are as follows:（1）The surface-fragmentating hyperbranched antifouling polymers（h-PCLx）were prepared via reversible addition-fragmentation chain transfer（RAFT）polymerization of methyl methacrylate（MMA）,tertiary carboxybetaine ester（TCB）and divinyl-functionalized poly（ε-caprolactone）（PCL-V₂）.With the increase of PCL-V₂ content,the branching degree of h-PCLx increased from 0.7 to 4.6,and the hyperbranched structure improved the crystallinity of PCL.Attenuated total reflection Fourier transform infrared（ATR-FTIR）test shows that after immersion in 0.1 M Na OH solution for 3 h,the hydrolysis of TCB generates hydrophilic zwitterions.The water contact angle（WCA）test reveals that the WCA of the coating was decreased after hydrolysis,further confirming the generation of hydrophilic surface.The adhesion test demonstrates that the adhesion strength of all coatings to the substrate before and after hydrolysis was greater than 1 MPa,indicating that the coating has good mechanical properties.Quartz crystal microbalance with dissipation measurements indicate that the polymer has a controllable degradation performance,and its degradation rate can be controlled by the PCL content.The higher the PCL content,the faster the degradation rate.Meanwhile,the polymer generates zwitterions by hydrolysis,exhibiting excellent anti-protein adsorption performance.Antibacterial and anti-diatom assays show that the polymeric coatings inhibit the adhesion of the marine bacteria Pseudomonas sp.and the diatoms Navicula incerta.（2）The effect of the type and content of divinyl monomers on polymer properties was further studied.We used divinyl monomers such as ethylene glycol dimethacrylate（EGDMA）,methacrylic anhydride（MAAH）and N,N?-adipic acid bis（diacetone acrylamide hydrazone）（DAA₂H）,and combined them with TCB and MMA are polymerized via RAFT polymerization to prepare self-regenerating zwitterionic hyperbranched polymers with adjustable degradation,respectively.The WCA test shows that the WCA of the coating first decreases and then stabilizes with the immersion time,and the value decreases with the increase of MAAH content;while the change of the cross-linker,the initial WCA of h-EGDMA3,h-MAAH3,and h-DAA₂H3 are about 78,79,and 81°,respectively,indicating that the type of cross-linker has slight effect on the initial WCA of the polymer.The ATR-FTIR test shows that the hydrolysis of TCB and degradation of cross-linker occurred on the coating surface simultaneously.The hydrolysis degradation test reveals that the degradation rate of the coating becomes faster with the increase of MAAH content,the degradation rate from slow to fast is h-MAAH0<h-MAAH3<h-MAAH6;and the degradation rate of cross-linker from fast to slow is DAA₂H>MAAH>EGDMA.The surface morphology test indicates that hydrolytic degradation causes the coating surface to become rougher with the increase of immersion time.The surface roughness of h-MAAH3 gradually increases from about 0.07 to 0.57μm,the surface roughness of h-DAA₂H3 increased from about 0.08 to 1.71μm.The antifouling assay shows that the coating can effectively inhibit the adhesion of bacteria and diatoms.As the immersion time increases,more and more zwitterions are generated by the hydrolysis of TCB,and fewer and fewer bacteria and diatoms adhere to the surface of the coating,and they were hardly observed after 7 days,indicating that the polymer has excellent antifouling properties.