Study On Dynamic Polymers With Two-dimensional Orthogonal Dynamic Properties Base On Acylhydrazone Bond And Disulfide Bond

Dynamic covalent polymers are polymers constructed by the dynamic covalent bonds.Such dynamic covalent polymers are endowed with smart properties because dynamiccovalent bonds are tunable formed and broken under external stimuli. This kind of dynamicpolymers has potential application values in drugs controlled release, active targeting drugscarrier, self-healing materials and so on.Acylhydrazone bond and disulfide bond are widely used reversible covalent bonds.Acylhydrazone bond responds to temperature and pH; while disulfide bond to light, pH andredox substances. Acylhydrazone bond and disulfide bond are compatible andnon-interfering within the same system, which is two-dimensional orthogonal. In this paper,through the condensation reaction of forming acylhydrazone bond, an amphiphilic triblockpolymer containing acylhydrazone bond and disulfide bond with smart properties has beensynthesized by combination the atom transfer radical polymerization (ATRP) with terminalfunctional modification and click chemistry reaction. Moreover, the paper explores thetwo-dimensional orthogonal dynamic properties of the amphiphilic triblock polymer underthe stimulus of different pH and redox species. The main contents of this paper are asfollows:1. Synthesis of,-dialdehyde-terminated telechelic polystyrenes: dibromo-terminatedfunctional initiator ((BiBOE)2S2) are used to synthesize,-dibromo-terminatedpolystyrenes(Br-PS-Br) with narrow molecular weight distribution by atom transfer radicalpolymerization (ATRP), and then get dialdehyde-terminated telechelic polystyrenes byazidation and click chemistry reaction. Simple and efficient azidation and click chemistryreaction avoid the generation of terminal olefin during functional groups conversion andpolymers with low molecular weight are in favor of the terminal aldehyde functionalization.This provides favorable conditions for the efficient reaction of polymers containingaldehyde group with substances containing amino, hydrazine, and aminoxy.2. Synthesis of hydrazide-terminated polyethylene glycol monomethyl ether:polyethylene glycol monomethyl ether CH3O-PEG-OH is modified to hydrazide-terminated polyethylene glycol monomethyl ether CH3O-PEG-NHNH2by the method of esterification, nucleophilic substitution and hydrazinolysis reaction of ester withmethanesulfonyl chloride, the terminal functionality of each step is close to100%.3. Synthesis of amphiphilic triblock dynamic polymers: the terminal hydrazide ofpolyethylene glycol monomethyl ether and the terminal aldehyde of polystyrene arecondensed into acylhydrazone bond of amphiphilic triblock polymer: polyethyleneglycol-b-polystyrene-b-polyethylene glycol (PEO-b-PS-b-PEO) with acylhydrazone bondand disulfide bond.4. Study on smart properties of amphiphilic triblock dynamic polymers: amphiphilictriblock dynamic polymer PEO-b-PS-b-PEO containing acylhydrazone bond and disulfidebond can be self-assembled in dilute solution of N, N-dimethylformamide (DMF) and water.Meanwhile, based on two-dimensional orthogonal dynamic properties of acylhydrazonebond and disulfide bond, such self-assembled amphiphilic triblock dynamic polymerssystem not only can undergo reversilble transformation of self-assembled aggregates underthe stimulus of different pH, but also show the dynamic characteristics in the presence ofreductant-oxidant Bu3P-O2.