Preparation And Characterization Of Luminescent Cyanostilbene Materials

Aggregation-induced emission(AIE)materials show weak or no light emission in dilute solution state,but have strong fluorescence intensity in aggregated or solid film states.The application of AIE effect to luminescent molecules is expected to solve the inherent contradiction between ordered self-assembly and emission property.As a kind of typical AIE molecules,cyanostilbene derivatives'chemical structure and optical properties can be easily adjusted,which have wide application prospect in the fields of chemical sensing,biological probes,and opoelectronic devices.So it has important scientific significance and application value to prepare cyanostilbene-based small molecules and polymers with AIE property through the molecular design and adjustment.In this dissertation,the cyanostilbene derivative with dendritic tails was synthesized,and then it was introduced into the polymer system as the liquid crystalline mesogen to prepare a series of side-chain liquid crystalline polymers.The optical properties and aggregated structures were studied in detail.The main research contents are as follows:(1)A kind of cyanostilbene small molecule(CN-DBE)containing dendritic tail chains was designed and synthesized.The luminescence and photoisomerization properties of the sample were investigated by UV-Vis absorption spectroscopy and fluorescence emission spectroscopy.The experimental results show that CN-DBE has typical AIE property,the photoisomerization phenomenon can occur under UV lamp irradiation.The results of thermogravimetric analysis and X-ray diffraction reveal that CN-DBE has good thermal stability and can form long-range ordered crystalline structure.In addition,CN-DBE materials can also selectively detect aniline with rapid response and quantitative property,which has potential application in fluorescence sensors.(2)Through ring-opening metathesis polymerization reaction,a side-chain liquid crystalline polynorbornene(P-CN-DBE)was prepared by introducing cyanostilbene unit into the polymer system.The luminescence property and liquid crystalline structure of the polymer were investigated.The experimental results show that the polymer has typical AIE property and good thermal stability.The dendritic tails can improve the nano-segregation ability of the side chains,which facilitate the polymer to form lamellar liquid crystalline structure.(3)Based on hydrogen bonding interaction between poly(4-vinyl pyridine)(P4VP)and cyanostilbene derivative,a series of supramolecular liquid crystalline polymers P4VP(CN-DBE)_x(x is the molar ration of the small molecule to the repeating unit of P4VP)with AIE property were designed and prepared.The liquid crystalline structure of the P4VP(CN-DBE)_x system has significant composition dependence.For x=0.2,P4VP(CN-DBE)_x exhibits lamellar liquid crystalline structure;For x=0.4,0.6,0.8,P4VP(CN-DBE)_x possess columnar liquid crystalline structure.