Design And Study On Antifouling Coatings With Microphase-Separated Structure

The settlement of microorganisms on artificial surfaces immersed in sea water, usually termed as marine biofouling, has enormous harm upon ships and other sea facilities. Usually, the marine biofouling can be reduced markedly or resisted by the use of the antifouling coatings. However, with the time of ban of environmentally harmful tributyltin (TBT)-based paint products approaching, it is quite urgent to develop the environmentally friendly antifouling coatings. On the other hand, some marine animals (such as dolphin, whale, et al.) and plant leafage (such as lotus) have the capability to resist the biofouling (namely, self-cleaning effect) because of their micro-nano-binary structure. So materials with microphase-separated structure, namely, micro-nano-binary structure, may be used as marine biofouling coatings. Based on this idea, in this paper, via simulating the surface structure and property of the biology, combining the excellent protein-antifouling property of poly(ethylene glycol) (PEG) and low surface free energy of poly(dimethylsiloxane) (PDMS), several kinds of graft copolymer, block copolymer and binary polymer brushes with microphase-separated structure were designed and successfully synthesized. Then the surface properties, microphase-separated structure and protein-antifouling property of these coatings were investigated. The detail research contents and results are summarized as follows:1) A novel approach for synthesis of polydimethylsiloxane(PDMS)-based macroazoinitiator (MAI) was developed by direct polycondensation of hydroxyalkyl-terminated PDMS with 4, 4'-azobis-4-cyanopentanoic acid (ACPA). As compared to the traditional method for synthesis of MAI, only one-step reaction was involved and the synthetic reaction could be performed under extremely mild conditions, e. g., ambient temperature and moisture. Moreover, the resulted MAI had very high yield and initiation efficiency for initiating the polymerization of monomers. This synthetic method was so facile that it could be expected to extend for synthesizing various macroazoinitiators with diverse macromolecular segments, as well as various block copolymers.2) Poly(methyl methyacrylate)-block-polydimethylsiloxane (PMMA-b-PDMS) copolymers with various compositions were synthesized by the use of PDMS-containing macroazoinitiator (MAI) as initiator. And then the bulk and surface properties of the resulted block copolymers were characterized by the techniques such as DSC, GPC, TEM, XPS, AFM and contact angle measurements. Results showed that copolymers had distinct microphase-separated structure because of the incompatibility between PMMA and PDMS blocks. By contrast, the copolymer films took on a gradient of composition from the outmost layer to the interior and more PDMS segments enriched at the film surfaces, which then resulted in the low surface free energy and little microphase separation at the film surfaces. Slight crosslinking of the block copolymers led to much steady morphology and more distinct microphase separation, in particularly for copolymers with low content of PDMS.3) A series of amphiphilic PDMS-b-PEG block copolymers were successfully synthesized with MAI as initiator for polymerization of poly(ethylene glycol) methyl ether methacrylate(PEGMA) macromonomer. The properties of copolymers were investigated with ~1H-NMR, FTIR, DSC, GPC and contact angle measurements. Results indicated that block copolymers had distinct microphase-separated structure, and more PDMS chains enriched at the copolymer films because of the lower surface free energy of PDMS. The composition and surface morphology of the copolymer films changed when the copolymer met with water, which endowed copolymers with better protein-antifouling property.4) The binary polymer brushes (PMMA-PEG) were synthesized on 3-glycidoxypropyl trimethoxysilane(GPS)-modified silicon wafer from two immiscible polymers: poly(methyl methacrylate) (PMMA) and poly(ethylene glycol) (PEG), via the "grafting-to" approach. The surface composition, layer thickness, surface coverage, chain density, wetting ability, topographical morphology and protein resistance capability of the binary brushes were investigated by XPS, ellipsometry, AFM and contact angle measurement. The results revealed that both PMMA and PEG had been successfully grafted onto the GPS-modified surface, and the surface coverage, chain density of PMMA and PEG brushes could be controlled by modulating the reaction temperature and time. These binary polymer brushes exhibited distinct microphase-separated structure and property of excellent protein resistance. Further more, the more distinct of the microphase separation at the surface, the better of the protein resistance of binary polymer brushes.5) Polystyrene-graft-poly(ethylene glycol) copolymers (PS-g-PEG) were successfully synthesized by using the "grafting-through" method. The graft copolymers and the surface properties of their coats were investigated by ~1H-NMR, GPC, DSC, TEM, XPS, static contact angle measurement, and AFM technique. Both DSC and TEM indicated that the graft copolymers had microphase-separated structure. AFM showed the microphase-separated structure also occurred at the coat surface, especially for copolymers with high PEG content, which could also be indirectly confirmed by the XPS and contact angle results. The graft copolymers with distinct microphase-separated structure had better capability for resistance to protein, and the mechanism of the formation for microphase-separated structure and of the protein resistance was discussed in detail.