Structural Adjustment Of High Efficiency Luminescent Liquid Crystalline Polymers And Their Photophysics Property And Phase Structure

The luminescent liquid crystalline polymers(LLCPs)with sufficiently large molecular weight not only possess superior film-forming properties but they also show excellent polarization performance after orientation,which allows their wide application in optoelectronic fields,such as in organic light-emitting diodes(OLEDs),three-dimensional(3D)imaging systems,optical information storage systems,and so forth.Therefore,it is of great importance to fabricate novel LLCPs,which can not only emit high efficiency fluorescence,but also form all kinds of phase structures in mesophase.In this thesis,we prepared two aggregation-induced emission(AIE)-active liquid crystalline polymers(LCPs)by introducing TPE derivative.Further,we investigated the relationship of structure and performance and explored the optoelectronic properties of the LLCPs.In the first section,the monomer 2,5-bis[4??-(4?,4?-dibutyloxy)tetraphenylethylene]styrene(M1)and the copolymers poly{2,5-bis[4??-(4?,4?-dibutyloxy)tetraphenylethylene]styrene}_x-{[2,5-di(hexylformate)]styrene}_y(Pns,n=1,2,3)were designed and synthesized.The results of DSC,PLM and wide-angle X-ray diffraction(WAXD)reveal that M1 shows no LC property while three copolymers all present typical columnar liquid crystal phase(Col _H).Subsequently,we investigated the photophysical property of M1 and Pns by ultraviolet-visible absorption spectrometry(UV-vis)and fluorescence emission spectrometry(PL).The results indicate that M1shows AIE behavior while three copolymers exhibits aggregation-enhanced emission(AEE)property.In addition,M1 shows very strong solid state emission with a fluorescence quantum yield(?_F)of 27.7%whereas Pns exhibit solid-state fluorescence with?_F in the range 18.4?24.3%.The?_F value of the copolymers increases with the increasing contents of composition M1.However,due to the limit of the steric hindrance of M1,we can't obtain copolymer whose the content of M1 exceed 45%despite under harsh conditions.The obtained Pns with good solution processability can be used to prepare highly luminescent two-dimensional patterns with high resolution through nanoimprint lithography,which reveals that Pns find potential applications in advanced optoelectronic and biophotonic devices.In the second section,LLCPs with high-efficiency emission in the solid state,namely poly([3??-(4,4?-dibutyloxy)tetraphenylethylene]styrene)(PSTPE)was successfully prepared through radical polymerization under mild conditions.The chemical structures of the monomer and polymer are identified via nuclear magnetic resonance(NMR),MALDI-TOF MS and gel permeation chromatography(GPC)characterization.Meanwhile,the results of WAXD analysis reveal that the PSTPE can form typical smectic phases.The results of UV and PL reveal that both monomer and polymer show AIE behavior.More interestingly,polymer shows higher emissive efficiency after thermal annealing.Further,the results of WAXD and UV-vis studies indicate that the polymer can form more ordered structures after thermal annealing,which means that an increase in ordering can enhance emission.