含氟及手性交联剂的液晶弹性体的合成与性能

合成向列液晶单体:4-((4-烯丙氧基)苯甲酰氧基)苯基-4-氟苯甲酸)酯(M1)和非液晶手性交联剂:双(4-((4-烯丙氧基)苯甲酰氧基)异山梨醇酯)(MC).按不同比例将M1和MC接枝共聚到聚甲基含氢硅氧烷上,得到含氟手性液晶弹性体PI~PVIII.用红外光谱、核磁共振表征单体和聚合物结构,用差示扫描量热仪、热失重仪、偏光显微镜及X射线衍射等手段研究其液晶性能.结果表明,含氟类短而硬的液晶基元更易被手性诱导,出现性能优异的胆甾相.其中,PI为向列型液晶,PII~PVII为出现油丝和Grandjean织构的胆甾型液晶,PVIII没有液晶性.弹性体玻璃化转变温度随着手性交联剂含量的增加先增大后减小,熔点和清亮点均呈下降趋势.所合成的液晶弹性体热稳定性好,质量损失5%时的热失重温度均在300℃以上.

Synthesis and Properties of Liquid Crystal Elastomers Containing Fluorine and Chiral Crosslinking Agent

Nematic monomer: 4-(4-(allyloxy)benzoyloxy)phenyl 4-fluorobenzoate (M₁) and non-liquid crystalline crosslinking agent: bis((4-(4-allyloxy)benzoyloxy)isosorbide benzoate)(M_C) were synthesized. M₁ and M_C with different proportions reacted with polymethylhydrosiloxane and chiral liquid crystalline elastomers containing fluorine PI-PVIII were got. The chemical structures and mesomorphic properties of monomers and elastomers were studied by means of FT-IR， ¹H NMR， POM， DSC， TGA and X-ray. The experiment results showed that short-hard liquid crystal elements containing fluorine could be induced into cholesteric phase with wonderful properties. PI presented nematic phase and PII-PVII displayed cholesteric phase with oily-streak and Grandjean texture. PVIII did not have any liquid crystalline properties. The glass-transition temperature increased first and then decreased， whereas both the melting point and clearing point decreased. The synthesized liquid crystal elastomers had good thermal stability， and the thermal weight loss temperature was greater than 300℃ with only 5% weight lost.