Synthesis And Characterization Of Cholesteric Azo Liquid Crystal Polymers

Azo liquid crystal polymers are promising materials for optical information storage,optical switching and nonlinear optical equipment because of their photo isomerization and photochromic.So they have received much attention at home and abroad in recent years.In this paper,one kind of cholesteryl liquid crystal mononter M1 and one kind of single phenol monomer M2,two kinds of cyano-containing monomers M3 and M4,and one kind of azo liquid crystal mollomer P.The MPA series polymer was obtained by copolymerization of M1 and M2,and the MQA and MRA series polymers were obtained by copolymerization of M1,M2 and M3,M4.MPA,MQA and MRA have the same main chain length.Three series of azo liquid crystal polymers MPZ,MQZ and MRZ were synthesized by esterification of precursor polymers MPA,MQA and MRA with azo liquid crystal mollomer P.Some conventional experimental analytic techniques were used to comfirm the chemical structures and liquid crystal properties of monomers and polymers such as FTIR,POM,DSC,XRD and ultraviolet-visible,showing that the structures were in line with the molecular design.From the UV-Vis,the azo polymers of MPZ,MQZ and MRZ are compared with their precursor polymers MPA,MQA and MRA series,MPZ.MQZ and MRZ have absorption peaks at 360 nm and 460 nm and the values become larger as the corresponding azo content increases.The cis-trans isomerization of the polymer occurs under illumination.Stop lighting and return to the state before lighting.It is indicated that all three series of azo polymers have photochromism.By DSC curve,all the heating and cooling curve of liquid crystal monomers appeared melting point and clear point.The temperature rise curves of the precursor polymers MPA,MQA and MRA series and the azo liquid crystal polymers MPZ,MQZ,MRZ series show obvious glass transition temperatures.The Tg of the MPA series gradually decreased,and Ti gradually increased,the Tg and Ti of the MQA series gradually decreased;the Tg of the MRA series decreased first and then increased,and Ti gradually decreased.The Tg of MPZ series gradually decreased,Ti increased gradually.the Tg of MQZ series increased gradually,Ti increased gradually,the Tg of MRZ series increased gradually,and Ti gradually decreased.It was confirmed by POM that the monomer M1 showed oily-streak texture,which was a cholesteric liquid crystal monomer,and the monomer P showed pherulite texture and was a smectic liquid crystal monomer.The three series of polymers have a wide range of liquid crystal phases,their liquid crystallinity is characterized by a special color texture,and all polymers are thermally induced and mutually denatured liquid crystal polymers.The precursor polymers MPA,MQA and MRA belong to the cholesteric liquid crystal,the polymers of the azo liquid crystal polymers MPZ,MQZ and MRZ series showed distinctly bright color texture.As the color diversity of the polymer gradually decreases,the red color gradually dominates and showed the cholesteric liquid crystal.The precursor polymers MPA,MQA and MRA series and the azo liquid crystal polymers MPZ,MQZ and MRZ series are all dextral optically active substance measured by polarimeter.As the chiral monomer content inreases,the optical rotation of the polymer also increase.From XRD,it is further proved that the synthesized precursor polymers MPA,MQA and MRA series,azo liquid crystal polymer MPZ,MQZ and MRZ series are consistent with the cholesteric polymer parameters,indicating that all polymer series belong to cholesteric phase.