High Efficiency Luminescent Liquid Crystalline Polymers Based On Aggregation-Induced Emission And "Jacketing" Effect:Design,Synthesis,Photophyscial Property,and Phase Structure

In this thesis,a series of high efficiency luminescent liquid crystalline polymers(LLCPs)based on aggregation-induced emission(AIE)and "Jacketing" effect were successfully designed and synthesized using tetraphenylethylene as the side group.Herein,we focus on the relationship between the supra-molecular structures and photophisical property.First,we designed and synthesized two series of LLCs contained TPE derivate,2,5-bis{[2-(oxy-tetraphenylethylene)4,4-2-(j-alkyl)]oxycarbonyl }styrene(denoted as Mj,j represents the number of carbon in the alkyl tails and j= 0,2,4,6,8,10,12.)and 2,5-bis{[2-(4-oxy-tetraphenylethylene)k-alkyl]oxycarbonyl} styrene(denoted as Mk,k represents the number of carbon in the alkyl spacers and k= 2,4,6,10,12).The corresponding polymers Pj and Pk were abtained via radical polymerization.The chemical structures of the monomers and the corresponding polymers were confirmed by 1HNMR,13C NMR and fourier transform infrared spectroscopy(FTIR),Mass spectral and elemental analysis(MS).The thermal stability investigated by thermogravimetric analysis(TGA).It has been demonstrated that these PLLCs have excellent thermal stability.Combined results of differential scanning calorimetry(DSC),polarized light microscopy(PLM),one-dimensional wide-angle X-ray diffraction(1D WAXD)and Pk-TPE showed Pj-TPE form SmA phase,and the d-spacing of the layer is increasing with increasing the alkyl tail length.The luminescent properties of compounds were studied by the UV-Vis absorption spectra,photoluminescence spectra(PL).The results comfirm that monomers have aggregation-induced emission(AIE)effect and polymers show aggregation-induced enhanced Emission(AIEE)effect.Due to PET process the quantum yields(OF's)are quenched to a very low value.ForPk,the photophysical properties and phase behavior were investigated via various techniques such as UV-Vis absorption spectra,photoluminescence spectra(PL),polarized light microscopy(PLM),differential scanning calorimetry(DSC),variable temperature one-dimensional wide-angle X-ray diffraction(1D WAXD).The results revealed that all resultant monomers show typical AIE behavior and the polymers exhibite aggregation enhanced emission(AEE)behavior.Moreover,because of "Jacketing effect",the polymers showe high efficiency luminescence in liquid crystalline state,which are significantly dependent on the spacer length(The solid-state quantum yields decrease from 52%to 18%with increasing spacer length).Meanwhile,the glass transition temperatures(Tg)decrease with increasing the length of spacers.With increasing the spacer length,the phase structure transforme from smectic A(SmA)(Pk,k= 2,4,6)to hexagonal columnar phase(ColH)(Pk,k =8,10,12).