| Liquid crystal elastomer materials are a new generation of polymer materials based on traditional elastomers and polymer materials for molecular design,introduction of liquid crystal phase and thermodynamic steady state.The liquid crystal elastomer material has both the anisotropy of the liquid crystal and the rubber elasticity of the polymer network.Compared with the non-crosslinked liquid crystal polymer,the liquid crystal elastomer has a unique soft elasticity.The chiral liquid crystal elastomer imparts more excellent properties due to its helical structure.It not only has excellent mechanical properties,thermal and chemical stability of general elastomers,but also ferroelectricity,piezoelectricity due to chirality.These properties make it a potential application prospect in display,piezoelectric,nonlinear optics,and non-porous permeable membranes.In this paper,a liquid crystal monomer A containing cholesteric alcohol,two monophenolic monomers M,N,two chiral crosslinkers P,R,and a liquid crystal crosslinker Q were synthesized.A,M and Q were copolymerized to obtain AMQ series elastomeric polymer;A,N and Q were copolymerized to obtain ANQ series elastomeric polymer;A,N and P were copolymerized to obtain ANP series elastomeric polymer;A,N and R were copolymerized to obtain ANR series elastomeric polymer.Four series of cholesteric liquid crystal elastomers AMQ,ANQ,ANP and ANR were finally prepared.Some conventional experimental analytic techniques such as FT-IR,1H-NMR,DSC,POM,crosslink density test,selective reflection test,XRD were used to comfirm the chemical structures and liquid crystal properties of monomers and elastomers,which indicating that the structures are consistent with molecular design.From the DSC curve,it can be seen that the temperature rise and fall curves of the monomers A and Q all have correspondingly sharp melting points and clearing points.The temperature rise curves of the elastomeric polymers AMQ,ANQ,ANP and ANR series showed obvious glass transition temperatures,and someone whose clear spots are not obvious can combine with POM for analysis.Both Tg and Ti of the AMQ and ANQ series show a gradual increase trend,which show that the crosslinker Q increased the Tg and Ti of the liquid crystal elastomer.Comparing the Tg and Ti of the AMQ and ANQ series,the increase in the content of the monophenol monomer makes the Tg and Ti of the ANQ series gradually lower than the AMQ series,that is,the long-chain monophenol monomer lowers the Tg and Ti of the liquid crystal elastomer.The Tg of the ANP series showed a gradual decrease trend,and Ti first increased and then decreased.The Tg of the ANR series showed a trend of decreasing first and then increasing,and Ti appeared to be gradually increasing.The crosslinker P promotes a decrease in Tg and Ti of the liquid crystal elastomer.The crosslinkinger R promotes an increase in Tg and Ti of the liquid crystal elastomer.By POM,both liquid crystal monomers have a distinct characteristic texture features.A is a cholesteric liquid crystal m onomer and crosslinker Q is a nematic liquid crystal monomer.The four series of elastomeric polymers have a wide range of liquid crystal phase temperatures and are thermotropically variable liquid crystal polymers.The liquid crystal property is a cholesteric liquid crystal which has a special color texture under pressure.By selective reflection experiments,it can be observed that four series of elastomeric polymers show different selective reflections under compression.By the optical rotation test,It is known that both chiral crosslinkers are left-handed optically active substances.From the swelling experiment,it can be seen that as the degree of crosslinking increases,the relative average molecular mass Mc between the cross-linking points decreases,and the cross-linking density Me of the liquid crystal elastomer increases.By XRD and the combination of POM and DSC analys,they show that all elastomers series belong to the cholesteric phase. |
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