Synthesis And Optical Performance Of Luminogenic Polymers With Aggregation-Induced Emission Characteristics Based On Tetraphenylethylene And β-cyclodextrin

With the discovery of aggregation-induced emission（AIE）fluorescent materials,the defects in application of traditional fluorescent materials due to the effect of aggregation caused quenching（ACQ）,have been successfully overcome.So it has been one of research focus in the field of organic light-emitting diodes（OLEDs）,fluorescent probes,and organic dye sensitized solar cell during the last decade.Tetraphenylethylene（TPE）is a typical AIEgen,so TPE and its derivatives have attracted more attention of researchers because of its numerous advantages,such as facile synthesis,easy functionalization,and remarkable AIE effect.Compared with the TPE small molecule,polymers based on TPE have a number of advantages,such as the combination of unique properties of polymer and AIE characteristic,easily giving emission response toward external stimulus.As a result,polymers based on TPE are more easily used to prepare all kinds of functional fluorescent materials.In recent years,another kind of new type AIE polymer gradually attracted the attention of the researchers,which does not containπ-aromatic building blocks such as benzene ring,thiophene,fluorene,and carbazole,but only containing auxochromophores or unconventional chromophores,such as aliphatic tertiary amine,ester,hydroxyl,and amide compared with the conventional luminescent polymer.Obviously,the molecular structure of this kind of polymer is closer to that of biomacromolecule.So,they possess better biocompatibility,stronger ability of endocytosis,and lower cytotoxicity,also show the potential application for fluorescent sensors and imaging.In this dissertation,we explored developing new functional AIE fluorescent polymer materials using a novel TPE derivatives initiator andβ-cyclodextrin（β-CD）,and explored providing a good vantage point and method to create novel AIE functional polymer luminescent materials.The main research content is as follows:（1）Using 4,4’-dihydroxybenzophenone as the starting material,we synthesized a new type of TPE derivative initiator containing four arms,and use it to prepare the counterion-sensitive（C lO₄^-,PF₆^-,TFSI^-）AIE polyelectrolyte microspheres（TPE-PMETAC）through covalently grafting of PMETAC and TPE by Atom Transfer Radical Polymerization（ATRP）.The component and structure of TPE-PMETAC was characterized by ¹H NMR,¹³C NMR,IR,GPC and SEM.AIE characteristic of TPE-PMETAC was proved by using the experimental result of the fluorescence of TPE-PMETAC aqueous solution increased with the concentration of TPE-PMETAC and the fraction of the poor solvent（THE）volume increased.In addition,the effect of three counterions on the flourescene of TPE-PMETAC was investigated in detail,and the result indicated that the fluorescence intensity of TPE-PMETAC progressively increased according to the counterion series C lO₄^-<PF₆^-<TFSI^-,which is in accord with the ability of exchanged hydrophilic C l^-by hydrophobic anions in the order of ClO₄^-<PF₆^-<TFSI^-.The mechanism of tuning fluorescence was determined by dynamic light scattering（DLS）,zeta-potentials and scanning electron microscopy（SEM）.We proved that the size of the microspheres and electrostatic repulsive forces between the microspheres were decreased by the addition of counterions result from the hydrophobic-induced collapse of the surfaces of the microspheres.As a result,the obvious increase in the fluorescence of TPE-PMETAC based on the aggregation of microspheres.In this research,we firstly achieved the fluorescence tuning of AIE flourscence molecule by added different counterions,also provided a good vantage point and convenient method to design and prepare fluorescence tunable materials.（2）By using 4,4’-azobis（4-cyanovaleric acid）to modify TPE,we successfully synthesized TPE derivative initiator（TPE-AZO）containing four arms,and a series of AIE TPE-polymers by using TPE-AZO as initiator.The obtained polymers include TPE-PS and TPE-PVK with conjugated groups;hydrophilic TPE-PNIPAM,TPE-PMETAC,TPE-PMAA,TPE-PMPEGMA,and TPE-PVP;and hydrophobic TPE-PMMA and TPE-PMA.The nine different TPE polymers exhibited different emission from 370 to 482 nm because of the impact of amphiphilic and chromophore interactions.By further study of the optical properties of TPE-polymers,we found that TPE polymers exhibit the advantages of better combining the AIE characteristic with unique properties of polymer,such as the aqueous solution of TPE-PNIPAM,TPE-PMAA,and TPE-PMATAC give emission response toward temperature,the p H value of solution,and counterions（C lO₄^-）,respectively.We developed a practical and versatile approach for the preparation of functiomal AIE polymers and a good vantage point to create novel AIE functional materials.（3）Under mild condition,we successfully synthesizedβ-CD dimer and poly（β-CD dimer）only containing noconventional chromophore（amide group and hydroxyl group）by simple preparation process.The component and structure ofβ-CD dimer and poly（β-CD dimer）was characterized by ¹H NMR,¹³C NMR,IR,GPC and SEM.AIE characteristic ofβ-CD dimer and poly（β-CD dimer）was proved by the experimental result of the fluorescence ofβ-CD dimer aqueous solution increased with the concentration ofβ-CD dimer and the fraction of the poor solvent（C₂H₅OH）volume increased.In further study of the optical properties ofβ-CD dimer,we found that the fluorescence emission originated from the intermolecular through-space conjugation of lone pair electron by the hydrogen-bonding self-assembly of amide and hydroxyl groups.These results demonstrate that in the absence ofπ-electron conjugated system,the AIEβ-CD luminescent derivative can be prepared by introducing the electron-rich units like oxygen and nitrogen atoms into the nonfluorescenβ-CD.This research provided a new route of synthesizing non-toxic and environmental protection atypical AIE fluorescent biomacromolecule,and make the AIE fluorescent materials better applied in the field of cell imaging,biosensing,and drug delivery.