Synthesis And Characterization Of Fluorinated Chiral Liquid Crystal Elastomer

The liquid crystalline elastomers (LCEs) is a system that associates elastic rubber state with liquid crystalline properties of Liquid Crystals organically. Especially for chiral LCEs, it not only has good mechanical property, thermal and chemical stabilities of ordinary elasto-mers but also owns their additional properties such as piezoelectricity, ferroelectricity and pyroelectricity result from the symmetry breaking brought by molecular chirality, and has po-tential applications in the fields of display materials、piezoelectric materials、nonlinear optic and imperforate osmotic membranes etc. The study on fluorinated chiral LCEs is not only enrich the content of LCPs, but also provides theoretical basis and novel thought for chiral LCEs with specially properties. Moreover, they provide necessary experimental data and technology to explore their application.In this dissertation, two fluorinated monomers (M1、M2) and one cholesteric mono-mer(M3) was synthesized, which include4-((4-(trifluoromethyl)phenoxy)carbonyl)phenyl4-((3-(4-(allyloxy)phenyl)propanoyl)oxy)benzoate(M1),4-((4-fluorophenoxy)carbonyl)phenyl4-((3-(4-(allyloxy)phenyl)propanoyl)oxy)benzoate(M2), cholesteryl4-allyloxy benzoate(M3). And also synthesizeone chiral crosslinking agent,which is3,5-bis((3-(4-(allyloxy)phenyl)prop-noyl)oxy)benzoic-cholesterol ester.(N). And synthesizing M、M2、M3and N with PMHS to obtained three series of side chain type liquid crystal elastomerwith different chemical structure and performance(P1、P2、P3). The chemical structures of the monomers, crosslinking agents, homopolymers, and elastomers were characterized by FT-IR and1-NMR. The results showed that the structure conform to the molecular design.The mesomorphic properties and phase behavior were investigated polarizing optical microscopy (POM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The special optical rotations were measured by a polarimeter. The results showed that the two fluorinated monomers (M1、M2) are typical nematic liquid crystal,and the cholesteric monomer(M3) is cholesteric crystal, and also the cross-linking agent is dextrotatory compound but is not liquid crystal.One of fluorinated liquid crystal elastomer (P1) are semi-crystalline polymer, the other (P2) is amorphous polymer.With the increasing of cross-linking agent, they change from ne-matic polymer to cholesteric liquid crystal elastomer.crystal texture of Grand-jean is appear in POM. Cholesteric liquid crystal elastomer P3is amorphous polymer, and also crystal tex-ture of Grand-jean is appeared in POM. Among the three liquid crystal elastomer (P1、P2、 P3), glass-transition temperature(Tg), normal melting temperature(Tm), clearing tempera-ture(Ti) are all present certain regularity with the increasing of cross-linking agent. With the increasing of cross-linking agent, is’s Tg,Tm,Ti are all first increased and then decreased for liquid crystal elastomer (P1). For P2, the Tg first sises and then down alternately. For liquid crystal elastomer (P3), Tg first decreased and then increased, while it is first increased and then decreased for T1. Furthermore, according to the result of TGA, the decomposed temperature of the elastomers are higher than310.0℃, it means that they all have excellent stability.