Preparation And Properties Of Bio-based Degradable Polyurethane Marine Antifouling Coatings

Marine biofouling is an inevitable problem in developing the marine economy,exploiting the marine resources and safeguarding the security of territorial sea.It arises from the adhesion and colonization of marine microorganisms,animals and plants on the surfaces immersed in seawater.Currently,using antifoulant releasing coatings is the major approach to combat biofouling.However,antifoulants not only are toxic to targeted and non-targeted marine organisms,but also accumulate in marine environment,causing adverse impacts on marine ecosystem.In this thesis,we focus on combating biofouling in an eco-friendly way.We have designed and prepared degradable bio-based polyurethane/natural antifoulant coating,degradable and hydrolyzable bio-based polyurethane/natural antifoulant coating,and degradable bio-based polyurethane with hydrolysis-induced zwitterions under the guidance of new antifouling strategy "from the nature,for the nature".The relationship between the surface wettability,mechanical and surface renewal properties,antifoulant release rate,antifouling performance of the coatings and their structures has been studied.The main results are as follows:(1)We prepared bio-based degradable polyurethane with PLA as soft segment,and constructed a natural antifouling coating system by incorporating natural product antifoulant butenolide into the polymer.The polymer has good compatibility with butenolide,and can be used as the carrier of butenolide to control its release.By using digital holographic microscope(DHM)and antibacterial experiments,the antifouling mechanism of butenolide was further studied.Butenolide can repel and decrease the irreversible adhesion of bacteria and realize highly effective anti-bacterial function but without killing them like known toxic antifoulant 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one(DCOIT).(2)We synthesized PLA-based degradable polyurethane with hydrolyzable pendant groups triisopropylsilyl acrylate(TSA)via thiol-ene addition and polyaddition reactions,and prepared eco-friendly antifouling coating by mixing the polymer with natural antifoulant butenolide.The coating has good adhesion strength,and can form dynamic surface during the immersion in artificial seawater(ASW)attributed to the continuous degradation in main chains and the hydrolysis in side groups.Hydrolytic degradation and butenolide release rate measurements show that the surface renewal rate of coating can be adjusted by varying the kinds of degradable soft segments and the content of hydrolyzable TSA groups.Thus,butenolide can be released in a continuous,stable and controlled manner.The synergetic effect of timely surface renewal and sustained release of butenolide endows the coating with excellent antifouling ability under static condition.(3)We synthesized a telomer of tertiary carboxybetaine ester(PCB)by free radical telomerization,and used it as chain extender to prepared PLA-based degradable polyurethane whose side chains can hydrolyze and generate zwitterions.The polymer has good flexibility and adhesion strength which can match with the fishnet.The contact angle and attenuated total reflection infrared spectroscopy(ATR-IR)tracking tests reveal that the coating surface changes from hydrophobic to hydrophilic due to the zwitterions induced by the hydrolysis after immersion in ASW.The coating with zwitterionic surface shows excellent antifouling performance in protein adsorption,bacteria and diatom adhesion experiments,and the antifouling abilitiy increases with the PCB content.Such system realizes antifouling function without the help of antifoulant,which is ecologically friendly.