Synthesis And Optical Performance Study Of AIE Polymers Containing Unconventional Chromophores

As the luminous materials in the lighting,display,electricity and aerospace and other industries have great potential for the development of luminescent materials has been a popular scientific research.Polymer luminescent materials are easier to form films,easier to decorate and have higher stability than small-molecule luminescent materials,and have become the focus of current research.However,most of the luminescent materials will have a decrease in fluorescence intensity at the time of aggregation,that is,aggregation-induced quenching(ACQ).Since the use of many luminescent materials is carried out in an aggregated state,the ACQ phenomenon greatly limits the practical application of the luminescent material.In 2001,the Academician Tang Benzhong found that the phenomenon of aggregation-induced fluorescence quenching(ACQ)was called aggregation-induced emission(AIE).Since the introduction of AIE,a large number of researchers have been attracted by this interesting phenomenon and broad prospects.Traditional organic fluorescent polymers have been widely used in chemical detection,solar energy conversion,cell imaging,etc.They are usually composed of conjugated backbone or?electron systems,covalently bonded to provide sufficient conjugation.However,these fluoropolymers also have some drawbacks,such as poor light stability,high cytotoxicity,non-biodegradable,poor water solubility and complex synthesis methods,which are very unfavorable for their practical application.In recent years,another class of light-emitting polymers gradually attracted the attention of researchers.Compared with the classical luminescent polymer,the structure of this type of light-emitting polymer does not contain the conjugated?electron system elements such as benzene ring,thiophene,fluorene and carbazole,and contains only some auxiliary groups such as-CONH-,C=O,-COOR and aliphatic amino.Because of the chemical structure of these polymers,the chemical structure of the luminescent polymer is closer to that of ordinary polymers with good water solubility and biocompatibility.Their chemical preparation process is simple,environmentally friendly and shows obvious advantages in biofluorescence imaging.In summary,it is of great significance to explore how to use a simple synthetic method to prepare a novel AIE fluorescent material with biocompatibility without conjugate?electron system groups,but only atypical chromophores.In this paper,several novel AIE fluorescent polymers containing only atypical chromophores were synthesized by simple synthesis method.The optical properties and AIE properties were studied.The main research contents are as follows:(1)In this study,G0.5,G1.0,G1.2 and G2.0 were synthesized by Michael addition reaction and amidation reaction with high concentration in the presence of cystine dihydrochloride(G0)as the core and branching point.Four different algebraic S-S-PAMAM dendrimers containing disulfide bonds.The structure of S-S-PAMAM dendrimers was characterized by FT-IR,MS,EDS and so on.The optical properties of S-S-PAMAM dendrimers and the dendritic macromolecules(G2.0)AIE nature.The results show that the fluorescence intensity is obviously enhanced with the increase of polymer algebra.The influence of concentration and poor solvent(acetone)on the fluorescence of S-S-PAMAM(G2.0)was studied.It was proved that it had AIE characteristics.In addition,because the S-S-PAMAM structure contains a large number of disulfide bonds,by adding dithiothreitol(DTT)under mild conditions can be cut off,cracked into small molecules such as cystine fragments.Therefore,the S-S-PAMAM dendrimers synthesized by us have excellent biodegradability and AIE luminescence properties,which are expected to be used in fluorescence imaging and biological sciences.(2)The mono-[6-(divinyltriamino)-6-deoxy]-?-CD(DTCD)is amidated with malonic acid,dithiodipropionic acid and glutamic acid,respectively.Three novel biocompatible?-CDdimerswithAIEeffectweresynthesized:malonate-?-cyclodextrin dimer(PCD),3,3'-dithiodipropionic acid-?-cyclodextrin dimer(DCD)and glutamate-?-cyclodextrin dimer(GCD).The structures of three?-CD dimers were characterized by ~1HNMR,FT-IR and MS.The optical properties of the three?-CD dimers were systematically studied.The results showed that PCD,DCD and GCD could emit strong blue-green fluorescence,and the emission wavelengths were the same,and the order of fluorescence intensity was PCD>DCD>GCD.And the effects of temperature and pH on the fluorescence and temperature of~1HNMR and SEM were used to explain the luminescence mechanism.The hydroxyl groups,imino groups and amide groups in the dimer structure could form stable intermolecular hydrogen bonds.When many hydrogen bonds in the molecule interact,more help in the formation of aggregates between molecules,so that the formation of rigid structure within the molecule.This contributes to increasing the rotational resistance in the molecule,reducing the attenuation of the excited non-radiative energy,thereby increasing the fluorescence intensity.In addition,the three dimers can also form hydrogels,the gel can emit strong yellow green fluorescence.Compared with the previously reported AIE molecules,the?-CD dimer contains only atypical chromophores,more importantly,a good water-soluble,flexible chain,structural adjustable.This study provides a new idea for the preparation of non-toxic and environmentally friendly atypical AIE fluorescent biomacromolecules,so that AIE fluorescent materials are better used in cell imaging,biosensing and drug delivery.(3)Poly(isobutylene-alt-maleic anhydride)and mono-[6-(divinyltriamino)-6-deoxy]-?-CD(DTCD)are amidated.A polymer(PIMA-NH-CD)with aggregation-induced emission?-cyclodextrin(?-CD)was synthesized.The structure of the polymer was characterized by ~1HNMR,FT-IR,MS and so on.The luminescent properties of the polymer were systematically studied.The results show that PIMA-NH-CD has good water solubility,can emit strong blue-green fluorescence and has AIE effect.The PIM-NH-CD studies with AIE properties show that the addition of conjugated?-electrons is not only introduced into the?-CD by the addition of electron-rich groups such as nitrogen atoms and oxygen atoms,but also the?-CD derivative.This study provides a new idea for the preparation of non-toxic and environmentally friendly atypical AIE fluorescent biomacromolecules,so that AIE fluorescent materials are better used in cell imaging,biosensing and drug delivery.