In-Situ Visual Monitoring Of Nitroxide-Mediated Polymerization By Aggregation-Induced Emission Technique

Nitroxide-mediated polymerization(NMP)is a classic controlled/living radical polymerization technology,which is usually used to synthesize homopolymers and copolymers with controlled molecular weight and complex structure.Owing to the regulation of nitroxides,a reversible dynamic equilibrium can be established between the growth free radicals and the dormant species(alkoxyamine).The concentration of the growth radical can be kept at a low level,so that diradical termination reactions are avoided and the polymer chain can continue growing to polymers with high molecular weight.NMP gradually developed from the two-component initiator system of nitrogen oxygen radical and initiator to the single-component initiator system of alkoxy amine,and the structures of the regulating agent were also constantly explored during this process.One of the most important development is introducing functional groups into the structure of the nitroxides/alkoxyamines,which can bring nitroxides/alkoxyamines more functions such as: temperature sensitivity,light sensitivity,p H responsiveness,etc.In this thesis,we introduced tetraphenylethylene(TPE)groups,a typical molecular with aggregation-induced emission(AIE)character,to the structures of nitroxide/alkoxyamine.The NMP process could be monitored visually by the change of fluorescence intensity caused by the variation of system viscosity during the polymerization process.This method provides a novel sight to study NMP polymerization kinetics from optical perspective,and can also be used for rapid noninvasive monitoring of industry polymer production process.In addition,the obtained polymers also have AIE character,which have potential application in the fields of fluorescent coatings,biological imaging and polymer fluorescent probes.Following are the main contents of this thesis:(1)NMP polymerization regulators with AIE function were designed and synthesized.By introducing TPE groups to the structure of nitroxide 2,2,6,6-tetramethylpiperidine 1-oxyl free radical(TEMPO)and alkoxyamine 3-(((2-cyanopropan-2-yl)oxy)(cyclohexyl)amino)-2,2-dimethyl-3-phenylpropanenitrile(Dispolreg 007),the regulators TEMPO-TPE and Dispolreg 007-TPE were synthesized respectively.(2)The NMP of styrene monomer were carried out with TEMPO-TPE and benzoyl peroxide(BPO),and the NMP of styrene and MMA were carried out with Dispolreg 007-TPE.In the process of polymerization,AIE molecules were linked at the end of the molecular chain with the nitrogen and oxygen groups,and gradually showed the photoluminescence effect with the increase of the viscosity of the system.The fluorescence changes of the system in the polymerization process were analyzed,and the relationship between fluorescence intensity and the polymerization process was established by combining the monomer conversion and polymer molecular weight,in order to realize the visual monitoring of the NMP polymerization process.(3)The NMP of poly(ethylene glycol)methacrylate(PEGMA)was carried out with Dispolreg 007-TPE,to produce polymer fluorescence probe with AIE property.The fluorescence probe was then mixed with PLA by co-precipitation.Based on the self-assembly behavior of the polymer probe in aqueous solution,we realized the insitu visual monitoring of the hydrolysis process of PLA under basic condition.