Preparation And Performance Study Of New Polymer Coatings For Surface Modification Of Titanium Alloys

Due to numerous merits such as high toughness,low density,excellent biocompatibility and comparable elastic modulus with human native bone tissues.titanium based alloys have been widely used for biomedical applications including artificial joints,dental implants,and other hard tissue regenerative materials.However,the intrinsic bioinert,as well as the lacking of anti-bacterial and blood compatibility,titanium alloy based implants cannot guid the regeneration of new tissues,and be apt to cause infections and form thrombus after the implantation,resulting in the final falure of the implantation.Therefore,the improvement of the bioactivity and the bio-functionalility of the titanium-based implants is one of the remaining challenges in the clinical medicine,and the R&D of new titanium based biomaterials to meet specific requirements is the hot research area in the biomedical engineering field.Surface modification is a promising strategy to improve the bioactivity and bio-functionality of the biomaterials.Through facile modification either changing the surface morphology or binding bioactive molecules or functional mateirals on the surface could significant enhances the bioactivity of the substrates without compromising the bulk propertiesIn the current study,four types of novel metal tetherable zwitterionic-phosphonate(or phosphonic)copolymers.mainly beased on the strong coordination between the phosphonate or phosphonic motif and the metal surface,have been prepared for improving the anti-biofouling ability of the titanium substrate.In the meantime,through a phosphonic type of tatherable initiator that immobilized on the titanium surface,active-ester containing polymeric brushes has been grafted on the surface of titanium alloy.The research contents are listed as follows:(1)A diethyl(methacryloyloxyl)phosphonate monomer was synthesized.Based on the NMR characterizations,the effects of three purification processes on the purity of the monomer were compared.The ATRP and RAFT of DEMMP monomers were performed.The kinetic studies of these two controlled radical polymerizations revealed that RAFT polymerization exhibited a better-controlled manner.(2)A(methacryloyloxyl)phosphonic acid monomer(MMPA)was synthesized through the hydrolysis of DEMMP monomer.Combined with zwitteironic SBMA monomer,three types of novel copolymers with varied mol.ratios(SBMA v.s.MMPA.9:1,8:2,6:4)between the two monomers were prepared by using APS and TEMED as the initiator and catalyst,respectively.In the meantime.a novel block polymer,pDEMMP-b-pSBMA,was prepared by RAFT process based on the previously optimized conditions.Furthermore,the four types of copolymers were coated onto the surface of titanium alloy.Static contact angle measurements and XPS revealed the succsful fabrication of zwitterionic/phosphonate(phosphonic)copolymer on the metal surface.Protein adsorption test and platelet adhesion measurements indicated that all four types of zwitterionic/phosphonate(phosphonic)copolymers generally significantly improved the anti-biofouling ability of the titanium substrates.The prelimilary comparison between the three random copolymers and the block copolymer showed that the later copolymer is superior to the three random copolymers in improving the anti-biofouling ability.(3)A mathacrylic acid N-hydroxysuccinimide ester monomer(NHSMA)was synthesized.Through the kinetic studies of the ATRP of NHSMA under different temperatures,the polymerization parameters were optimized,and well controlled pNHSMA polymers(Mn=59200,PDI=1.07)were prepared.In the meantime,take advantage of SI-ATRP,pNHSMA brushes were succeefully fabricated on the surface of titanium.Furthermore,the activity of the active ester pendant on both the pNHSMA polymers and the pNHSMA brushes were verified by the coupling reaction with benzylamine.