Syntheses And Properties Of Aggregation-Induced Emission Active Liquid Crystals

Molecules with aggregation induced emission(AIE)property exhibit weak emission at the dilute concentration,but high emission in the aggregated state.The discovery of aggregation induced emission effect boosted the development of solid organic fluorescent materials.At present,there is few research on AIE active liquid crystal materials.By introducing liquid crystal function into AIE active materials,the novel functional molecules possessing excellent photophysical and mesophase properties with particular structures were obtained.It has directive significances to the design,synthesis and applications of novel fluorescent liquid crystal materials.In this paper,by using diphenylacrylonitrile derivative as the raw material and connecting liquid crystal units to AIE-groups through etherification and Schiff-based reaction,a series of fluorescence liquid crystal molecules were synthesized and their photophysical and mesophase properties were investigated.The main contents are as fo lows:Firstly,triphenylene Schiff bases with one,two or three diphenylacrylonitrile group(s)were designed and synthesized.Mesomorphic and fluorescence properties of these target compounds were investigated.The results indicated that the number of diphenylacrylonitrile group(s)can affect the mesomorphic and fluorescence properties.Secondly,three disarylacrylonnitriles-bridging triphenylene dimers were designed and synthesized.All these target compounds exhibited the ordered hexagonal columnar mesophases,intramolecular charge transfer effect and aggregation induced emission effect.Thirdly,cholestesterol group(s)modified diphenylacrylonitrile fluorescent liquid crystal molecules were designed and synthesized.The results suggested that hydrogen-bonds and the number of cholestesterol unit(s)can affect the mesomorphic and fluorescence properties.Fourthly,diphenylacrylonitrile derivatives with two,three,four or five fiexible chains were designed and synthesized.All these target compounds possess excellent AIE-luminescence property.The mesomorphic and fluorescence properties were affected by the number of alkyl chains.Finally,BODIPY dyes with one,two or three diphenylacrylonitrile group(s)were designed and synthesized.Performance testing indicated that there are two kind of energy transfer from diphenylacrylonitrile units to BODIPY groups for these target compounds and the stokes shifts were as large as 190 nm.