Design And Synthesis Of Specific Topological Polymers And Their Functionalization

Polymers with a specific topology have always been one of the hot spots in polymer research.Among them,branched polymers exhibit unique advantages because of their complex branching topology and abundant end groups.Similarly,as the unique cyclic topology,the cyclic polymers also have superior performance and broad application prospects in many fields.This article explored their synthesis methods and applications,as well as the relationship between topology and performance.The specific work was shown as follows.（1）Through the reversible addition-fragmentation chain transfer polymerization method,the serine protein（Spl B）enzyme-responsive branching agent（M-WELQK-M）,oligoethylene glycol ester methacrylic acid（OEGMA-OH）and oligoethylene glycol monomethyl ether polymethacrylate（OEGMA）,were copolymerized to prepare branched polymers.Then,branched polymers（WBPs）containing abundant thiol functional groups were successfully prepared by chemical reaction modification.enzyme-responsive silver nanoparticle aggregates（ANAs）were in situ synthesized by using the WBPs templates,silver nitrate as the sliver element provider,and sodium borohydride as the reducing agent.These synthesis processes were monitored,and the products were characterized in detail by various characterization methods.The experimental results showed that the enzyme-responsive ANAs,which consist of Ag nanoparticles,were stable and uniform.Subsequently,the antibacterial ability,antibacterial process,and response ability of ANAs were studied.The conclusions are as follows:when nearing the methicillin-resistant Staphylococcus aureus（MRSA）atmosphere,the branching agents were digested by the Spl B enzyme which were secreted by MRSA.Subsequently,the internal structure of the ANAs was destructed.Finally,MRSA were killed efficiently and effectively by the silver antibacterial agents that releasing from the collapsing ANAs.（2）The practical application of enzyme-responsive Ag nano-assemblies（ANAs）as wound dressings was evaluated from two aspects.1.Safety:The silver ions release process of ANAs in vivo has been simulated,firstly.The experimental results show that ANAs show negligible silver ion leakage in the simulated normal body environment.Subsequently,the safety of ANAs was evaluated at the cellular level,and the experimental results showed that ANAs exhibit better cell safety;2.Wound healing effect:the enzyme-responsive ANAs were promoted in MRSA infected rats and mice wound healing process.The experimental results show that enzyme-responsive ANAs possess better promoting wound healing effect.（3）First,the acid-responsive orthoester-based acrylate branching agent（OE-3）was successfully prepared.Subsequently,by atom transfer radical polymerization（ATRP）,OE-3,OEGMA,OEGMA-OH and diethylaminoethyl methacrylate were copolymerized to prepare an acid-sensitive branched block polymer（HP）.Using this polymer as a carrier,manganese dioxide nano-aggregates（HP-Mn O₂-NPs）were successfully synthesized successfully.Various characterization results confirmed the successful preparation of HP-Mn O₂-NPs.The changes of HP-Mn O₂-NPs under acid environment were examined in detail through dynamic light scattering（DLS）and transmission electron microscope（TEM）tests,which proved their acid responsiveness.（4）First,the ATRP functional initiator were prepared.Then,they were reacted with 3,4-dihydropyran（DHP）resin in an appropriate ratio for synthesizing the immobilized ATRP initiator（I₃）.Subsequently,the polymerization of the monomer butyl methylpropionate was initiated by I₃ for preparing isolated linear polymers with one end group fixed.Through the substitution of sodium azide,the linear polymer ends were successfully converted into azide groups.Subsequently,through a click chemical reaction and acid dissociation of the acetal bond,the linear polymers were changed into cyclic polymers.After separated from the DHP resin,the cyclic poly-n-butyl methacrylate with two different molecular weights was prepared.The polymerization products were characterized by various characterizations.The results proved that they were cyclic polymers.These results indicate that:the synthetic method could simply obtain cyclic polymers with high purity under high reaction concentration and is not required separation process.