Studies On The Controllable Surface Modification And Properties Of Polyvinyl Alcohol Membrane Based On PET-RAFT Polymerization

After the implantable medical materials enter the biological humoral environment,the attachment,aggregation,proliferation and differentiation of proteins,microorganisms,cells and other substances in the body fluids on the material surface will form biological pollution,which will affect the material's performance and thus limit its practical application.Some researches indicate that the initial behavior of microorganisms/cells on the surface of biomaterials is closely related to the surface structure and surface chemical properties of biomaterials.Based on various anti-fouling mechanisms,different surface modification strategies were proposed to improve the anti-fouling property of biomaterial.The controlled/living radical polymerization can be used to realize the graft copolymerization on the surface of materials,which can control the thickness,density,molecular weight distribution and functional composition of the grafted copolymer and has broad application prospects in the field of surface modification.PET-RAFT polymerization combines“photo-redox catalysis”and controlled/“living”radical polymerization.Its unique advantages of catalyst diversity,oxygen resistance and high chemical selectivity are expected to promote the industrial application of controlled/“living”radical polymerization in material surface modification.In this paper,we applied PET-RAFT in the modification of PVA-based hydrogels and prepared the modified PVA hydrogels through different functional substances.The structural characterization and comprehensive properties of the modified hydrogel were evaluated by ATR-FTIR,XPS,SEM/AFM,UV-Vis,TGA,mechanical and hydrophilic properties,as well as the biological properties of protein adsorption,cytotoxicity in vitro and the adhesion of eyelid fibroblasts.The main research contents and test results are as follows:1.The feasibility of PET-RAFT in PVA modification was preliminarily discussed with HEMA as the graft monomer.The grafting efficiency of Ru?bpy?₃Cl₂ and Eosin Y catalytic system were compared.Relevant test results show as follow:The optical transmittance of PVA-g-pHEMA was above 92.5%,and the initial decomposition temperature increased from 175.5?to 195.5?.Although the mechanical properties decreased with the increase of grafting degree,the overall tensile strength remained good.The water content also decreased regularly,but it still remained above 54.2%±1.48%.The surface hydrophilicity improved,and the water contact angle reduced from44.62°±2.93°to 29.68°±1.87°.In vitro,the cytotoxicity remained at grade 0 or 1.The anti-protein adsorption increased by 34.67%,while the cell anti-adhesion ability increased by 44.30%.2.Methylpropylene carboxylic acid zwitterion?CBMA?was synthesized by quaternary amination reaction,and CBMA was used as monomer to modify PVA hydrogel membrane by PET-RAFT polymerization technology.The influencing factors of graft copolymerization were discussed.The results showed that the graft percentage of the hydrogel membrane increased with the increase of CBMA monomer concentration and decreased with the increase of catalyst?Eosin Y?concentration and chain transfer agent?CPADB?concentration.The optimal reaction concentration was CPADB:1.20 mmol/L,eosin Y:0.03 mmol/L,and CBMA:358 mmol/L.The optical transmittance of PVA-g-pCBMA?Percentage of grafting less than 26.34%?remained above 91.2%.DTG data showed that decomposition peaks began to appear near126.4?,but the main decomposition temperature was 327.5?.Although the mechanical properties decreased with the increase of grafting degree,the overall tensile strength remained good.The comprehensive hydrophilicity of PVA-g-pCBMA improved with the increase of the percentage of grafting?0%⁵5.18%?,while water content can reach 78.23%±2.28%.and water contact angle decreased from 44.62°±2.93°to 18.06°±1.96°,about 59.52%.In vitro,the cytotoxicity maintained at grade 0or 1,and the anti-protein adsorption ability increased by 57.24%,while the anti-adhesion ability of cells increased by 61.03%.In the experiment,the corresponding relation between the content of N element and the graft percentage of CBMA actual mass was established;the conversion relation between the graft mass percentage?y?and the content of N element?x?was y=19.954x,R²=0.9977,thus greatly simplifying the determination method of graft percentage.In addition,by analyzing the causes of self-polymerization products in the experiment and combining with the polymerization mechanism of PET-RAFT,the reaction mechanism of grafting copolymerization modification of PVA hydrogel membrane by PET-RAFT polymerization technology was speculated.It was proposed that the process of grafting copolymerization occurred on the side chain hydroxyl of polyvinyl alcohol.3.Using glycidyl methacrylate?GMA?as the"bridge",using PET-RAFT polymerization technology and alka-catalyzed epoxy ring-opening reaction,chondroitin sulfate?Cds?was covalently grafted onto the surface of PVA hydrogel membrane.The modified PVA-g-pGMA and PVA-g-p?GMA-Cds?hydrogels were obtained.Relevant test results show:The optical transmittance of the sample decreases significantly?the transmittance of the visible region is 20-80%?.The mechanical properties also decreased to a certain extent,the tensile strength decreased from 3.42MPa to 2.31 MPa,and the elongation at break decreased from 495.06%to 225.26%,but it showed better flexibility in the range of elastic deformation.Although the water content affected by GMA was lower than that of the blank PVA hydrogel,it remained nearly 60%finally.The hydrophilicity of PVA-g-p?GMA-Cds?improved obviously.Water contact angle decreased from 44.62°±2.93°to 11.86°±1.31°,about 73.42%.It is close to the general requirement for super-hydrophilic surfaces?<10°?.In vitro cytotoxicity showed that the toxicity level of PVA-g-p?GMA-Cds?samples remained at grade 0.Besides,it showed the effect of promoting cell proliferation.The anti-protein adsorption ability increased by 56.80%,and the cell anti-adhesion ability ultimately increased by 27.11%.