The Preparation Of New Polymer Brushes And Reactive Polymeric Micelles

Polymer brushes are defined as densely grafted side chains attached to a surfaceor interface. Comblike or densely grafted brush （co）polymers have receivedsignificant attention over the past decades because of their unique structures andproperties. The previous work focus on the synthesis of polymer brushes withdifferent structure via various methods. In the thesis, dynamic polymer brushes hadbeen prepared on the polymer backbone and the surfaces of nanoparticles bycombination of ATRP and Dynamic Covalent Chemistry （DCC） via “grafting from”method. The dynamic properties at specially chemical contition had been researchedin details.Polymeric micelles can be formed by the self-assembly of block copolymers inselective solvent. The stability can be improved by introducing cross-linked structureinto some domains of micelles. The previous researches focus on the morphologyand stimuli properties of micelles. In this thesis, stable micelles with cross-linkedstructure at special domain had been prepared. And the reactivity and dissociation ofstable micelles can be achieved via the effective coupling reaction, like ClickChemistry and ATRC.1. Dynamic macromolecular brushes had been synthesized by the combinationof ATRP and DCC. ATRP initiators were introduced onto poly（acylhydrazide）backbone through the formation of dynamic covalent acylhydrazone bonds.PPEGMA side chains were synthesized by in-situ ATRP of poly（ethylene glycol）methyl ether methacrylate （PEGMA） via “grafting from” method. PPEGMA sidechains can be dissociated from and re-grafted to the polymer backbone via thedynamic break and rearrangement of acylhydrazone bonds at acidic condition.Fluorescence probe labeled macromolecular brushes can be synthesized by dynamicexchange with1-pyrenecarboxaldehyde. The clear structure of macromolecularbrushes and living property of the polymerization process can be confirmed by¹HNMR and GPC. The dynamic property of macromolecular brushes can be proved by the real-monitoring on the dissociation and re-grafting of PPEGMA side chains andthe fluorescence probe via GPC or FL spectrum. Our results offered a model researchfor the application of dynamic hydrazone bonds in polymer brushes, and also aversatile method to functionalize polymer brushes.2. Silica particles modified by cleavable PS brushes can be prepared by thecombination of DCC and ATRP via “grafting from” method, the linkage isacid-sensitive imine bond. Based on the dynamic property of imine bond,multi-functionalized and mixed PS/PMMA brushes modified silica particles had beenprepared via “grafting to” method. PS brushes can be cleaved from silica particlesunder acidic condition. TEM, TG and DLS were used to characterize the cleaved PSand silica particles. Moreover, aldehyde-modified fluorescence probe and aldehydeend-modified PMMA were grafted onto the surface of silica particles based on thedynamic reaction of imine bond under acidic condition. NMR, TG, UV, FL andFluorescence total of confocal microscopy were used to characterize. The resultssignificantly prove the dynamic property of imine bond, and offered a versatilemethod to prepare multi-functionalized silica particles step by step.3. Reactive core cross-linked polymeric micelles with PEG/PtBA mixed coronahad been induced by the click reaction between azide-modified Poly（ethyleneglycol）-block-poly（2-hydroxyethyl methacrylate）-block-poly（tert-butyl acrylate）triblock copolymer （PEG-b-（PBIEM-N₃）-b-PtBA） and dialkyne-modified RAFTreagents in DMF, the good solvent for polymer and RAFT reagents. Polymericmicelles with cross-linked PNIPAM cores and PEG/PtBA mixed corona wereobtained after in situ RAFT polymerization of N-isopropylacrylamide （NIPAM）inside the cores of reactive triblock copolymer micelles.¹H NMR, FTIR, DLS andTEM were used to characterize the structures of the micelles before and after RAFTpolymerization. The degradation of the micelles was also investigated in this research.This type of micelles can be used as a platform for RAFT polymerization.4. A new strategy to prepare stable micelles with cross-linked interface by theinterfacial ATRC process had been offered. It’s the first time to prepare polymericmicelles with cross-linked structure by ATRC reaction. Micelles with PtBA as cores,PEG as shells can be formed by the self-assembly of bromo-modified PEG-b-PHEMA-b-PtBA triblock copolymer （PEG-b-PBIEM-b-PtBA） in aqueoussolution. Stable micelles with cross-linked interfaces can be obtained after interfacialATRC in the presence of Cu（0） between the bromo groups located at the interfaces.The entirely hydrophilic stable micelles with PAA confined in the core domains andPEG as coronae can be prepared after hydrolysis of PtBA, which can be used to bethe templates for inorganic nanoparticles and loading of dye by iron-exchange.¹HNMR, FTIR, DLS and TEM were used to characterize the structures of the micellesbefore and after ATRC and hydrolysis.5. Micelles with PtBA as cores, PEG as shells can be formed by theself-assembly of azide-modified PEG-b-PHEMA-b-PtBA triblock copolymer（PEG-b-（PBIEM-N₃）-b-PtBA） in aqueous solution. After click reaction between theazide groups located at the interfaces of micelles and dialkyne-modified RAFTreagents, reactive polymeric micelles with cross-linked interfaces had been obtained.The RAFT reagents located at the interfaces can be used in the in-situ RAFTpolymerization of NIPAM to prepare polymeric micelles with PEG/PNIPAM mixedcoronal chains. The morphology change can be characterizated by TEM as the changein temperature.6. Poly（ε-caprolactone）-block-poly（ethylene glycol）-block-poly（ε-caprolactone）（PCL-b-PEG-b-PCL） triblock copolymers with biotin groups at thejunction points were synthesized based on a combination of click chemistry andring-opening polymerization （ROP）. PCL-b-PEG-b-PCL triblock copolymers withjunction points modified by alkynes were synthesized by using alkyne/hydroxyldifunctionalized PEG as macroinitiators in ROP of ε-caprolactone. Thenazide-modified biotins were grafted onto the junction points of triblock copolymersvia click chemistry. GPC and¹H NMR results indicated successful synthesis ofwell-defined triblock copolymers. Upon addition of avidin to the micellar solution,micelles aggregated together forming micellar aggregates due to the interactionbetween avidin and biotin. The avidin/HABA competitive binding assay also provedthe bioavailability of the biotinylated micelles to avidin.