Construction And Application Of Dynamic(Di) Selenide-Containing Cross-linked Polymers With Controlled Structure

C-Se and Se-Se bonds are classified as weak bond,they have rapid response to multi external triggers,such as light,oxidative or reductive environment,radiation and so on.Intruduced these functional group to the polymers,especially the cross-linked polymers,dynamic?di?selenide containing cross-linked polymers will be prepared.Recently,these polymers have attracted much interest for a wide range of application in biomedical materials.Domestic researchers have done much more work in control durg delivery,self-healing materials and smart multi-response materials.The current synthetic methods for?di?selenide containing polymers are mainly as follow:modification with?di?selenide after polymerization,polymerization and self-assembly of?di?selenide containing monomers,aminolysis-oxidative coupling of diselenocarbonate-end polymers.While with the development of polymer materials,especially in the biological field,higher requirements have been put forward for the materials.It is important to regulate and optimize the?di?selenide functional group in the polymers.So,find new sytheis strategy,for precise regulation of molecular weight,molecular weight disperse,amount of selenium containing functional groups even the topological structure of polymers,will certainly improve the research and application of selenium containing polymers.Based on this demand,the thesis focused on precision synthesis of selenium containing polymers and exploration efficient strategy to fabricate?di?selenide structure.This would contribute to the application research of?di?selenide cross-linked polymers.The detailed researches were summarized as the following:1.From seleno-mediated radical polymerization to seleno-containing branched polymers and dynamic hydrogelDiselenocarbonate-end capped hyperbranched copolymers and diselenide contained dynamic hydrogel were synthesized for the first time on the basis of RAFT-SCVP mediated by diselenocarbonates in one step.Copolymerization of O-?4-methoxyphenyl?Se-?4-vinylbenzyl?carbonodiselenoate?VBDSe?with vinyl monomers such as styrene,methyl acrylate,n-butyl acrylate,methyl methacrylate,and N-isopropylacrylamide afforded hyperbranched copolymers with variable branch length and degree of branching.Polymers were characterized by NMR,SEC and thermal analysis.Degree of branching depended on the ratio of monomer to VBDSe.Also,LCST of thermos-response hyperbranched poly?VBDSe-co-NIPAM?was tunable by the ration of monomer and VBDSe.A dynamic diselenide containing hydrogel was obtained from a hyperbranched PNIPAM via aminolysis and spontaneous oxidation in an open system.Because of the easy oxidative and reductive performance of Se-Se bond combind with thermos-response of PNIPAM,this hydrogel showed redox and temperature responses2.Dynamic diselenide-based hydrogel-dressing:preparation and performanceA one-pot synthetic methodology for dynamic diselenide-based hydrogel was developed.This was realized by the nucleophilic ring-opening of selenolactone with the amino groups in the main chain of poly?2-ethyl-2-oxazoline?hydrolysate.Hydrogel was prepared via an in-situ oxidation of the selenol functionalities polymer in the air.The hydrogel demonstrated good swelling behavier and mechanical performance,and adhered to the skin very well.A unique feature of the hydrogel is its capability to be dissolved on-demand in oxidative or reductive condition or exposed to light,allowing facile application in burn dressing removal for reducing the pain in dressing change.3.Dynamic covalent selenide bond containing degradable cross-linked polymerA new method for preparing degradable cross-linked polymer containing dynamic selenidewasdemonstrated.1,2-Bis?2,3,5,6-tetrafluoro-4-vinylphenyl?diselane?FVPDSe?was synthesized and used as both photo initiator and dynamic covalent cross-linker to prepare cross-linked polymers via photo initiated Iniferter-SCVP with vinly monomers such as styrene,methyl acrylate,n-butyl acrylate,methyl methacrylate.The reaction system only contained FVPDSe,monomer and solvent.Cross-link density of the network was tunable.After oxidation by hydrogen peroxide,the structure of cross-linked polymer obtained from copolymerizaiton of FVPDSe with styrene was carefully ananlysized by ¹H,¹³C,¹⁹F,⁷⁷Se NMR and SEC.In addition,the“livingness”of the obtained cross-linked polymers was also investigated.This mothed provided new idea for controlled synthesis of dynamic covalent cross-linked polymers.4.Degradable narrow disperse polymer microspheres by diselenide mediated precipitation polymerizationA facile,general,and efficient one-pot approach to obtain narrow disperse,highly cross-linked,hydrophobic polymer microspheres with uniformly selenide cross-linked structures by diselenide mediated precipitation polymerization was described for the first time.The simple introduction of iniferter mechanism into precipitation polymerization system allows the direct generation of uniformly cross-linked polymer microspheres.FVPDSe was used as both initiator and cross-linker.The polymerization system only contained FVPDSe,monomer and solvent.The polymerization parameters?including stirring rate,monomer loading,molar ratio of cross-linker to styrene,and polymerization time?have proven to show significant influence on the morphologies of the resulting polymer microspheres,which made it convenient to control the particle sizes by easily tuning the reaction conditions.Because of the weak C-Se bond,the microsphere was degradable.And hydrophobic performance of the polymer microsphere was characterized by contact angle.The microsphere should be“livingness”for the dynamic C-Se bond,and could be surface functionalization.This work riched the usage of living radical polymerization in precipitation polymerization,and made the synthesis of functional microsphere easier.