Synthesis And Characterization Of Chiral Liquid Crystalline Elastomer Containing Azo Groups

Azobenzene-containing liquid crystalline polymer combine the basic features of orientational-order and positional-order of azo liquid crystal molecules with physical properties of polymers.Azo liquid crystalline Elastomers combine unique optical properties of azo liquid crystal with good mechanical property,thermal and chemical stabilities of polymer networks,which have been an important research project in the field of azo liquid crystalline elastomers.Therefore,study on azo liquid crystalline elastomers holds not only important theoretical purpose,but also potential applications in numerous areas,especially in the fields of piezoelectric optical and electrical etc.However,to the best of our knowledge,little research on azo liquid crystalline elastomers has been reported.Therefore,it is necessary and interesting to study azo liquid crystalline elastomers,which is not only affluent in the content of azo liquid crystalline elastomers,but also provides theoretical basis and novel thought to synthesize azo liquid crystalline elastomers with special optical properties.Moreover,they provide necessary experimental data and technology to explore their application in piezoelectric and anti-fogery areas on azo liquid crystalline elastomers.In this paper,one kind of cholesteryl liquid crystal monomer M,one kinds of single phenol monomers N,one kind of azo liquid crystal monomer L and one kind of azo crosslinking agent J are synthesized.At the same time,one series of liquid crystal polymer precursor P1 and three series of azo liquid crystalline elastomers,P2,P3,P4 are synthesized.The FT-IR were used to characterize the structure of the four monomers and four series,showing that the structures are in line with the molecular design.By DSC curve,all the heating curve and cooling curve of M and L appeare corresponding and obvious glass transition temperature and melting point.The heating curves of precursor polymer P1,P2,P3 and P4 series appeare obvious glass transition temperature and melting point,showing that P1,P2,P3 and P4 series belong to semicrystalline polymers.As the change of composition,the Tg of P1 series rise first,and reduces again,while the T1 reduces gradually;the Tg of P2 and P3 series increases,and the Ti increases gradually;the Tg of P2 series reduces first,and rise again,while the T1 reduces first,and rise again.Measured by POM,all the two liquid crystal monomers have obvious texture features.M is cholesteric liquid crystal monomer,while L is nematic liquid crystal monomers.The four series,in addition to the self-assembled products,have wide temperature range of liquid crystal phase,whose liquid crystalline property are manifested on the special color texture,indicating that all the polymers are thermotropic and enantiotropic liquid crystalline polymers both in the process of heating and cooling.To the precursor polymer Pi series,the more the content of M1,the more obvious the texture is,and they even appear oily streak texture,indicating that the Pi series belong to cholesteric liquid crystal;The three series of azo liquid crystalline elastomers,P2,P3,P4 can see obvious and bright color texture.With the increase of the content of L,the colour diversity of polymers recedes,and red gradually dominates,showing that the three series belong to cholesteric liquid crystal.