Ester type banana-shaped liquid crystalline monomers: synthesis and physical properties
作者:Katalin Fodor-Csorba、Anikó Vajda、Antal Jákli、Christian Slugovc、Gregor Trimmel、Dietrich Demus、Eszter Gács-Baitz、Sándor Holly、Giancarlo Galli
DOI:10.1039/b400246f
日期:——
New ester-type banana (bent-shaped) monomers, 1,3-phenylene bis[4′-(alken-1-yloxy)-biphenyl-4-carboxylate]s Ia–Vb, with different substituent(s) on the central phenyl ring (H, CH3, Cl or NO2) and alkenyl tails in the side arms (decenyl or undecenyl) were prepared. The analogues IIIa–IVb with 4-chloro- or 4,6-dichloro-substituents exhibited a nematic phase, while Va,Vb with 2-nitro-substituent showed a B7 phase at relatively low temperature. All the compounds were stable, no degradation or polymerization was observed under applied electric fields or heat treatments. Electro-hydrodynamic instabilities were observed in the nematic phase of each sample. In the B7 phase of Vb there was an electro-optical switching in the range 112–114.5 °C with a switching time of about 150 µs at 20 V µm−1 field. At lower temperatures no electro-optical switching occurred, but a ferroelectric-type spontaneous polarization of 22 nC cm−2 could be detected. The bend angle was calculated by the semiempirical CAChe/MOPAC/PM5 method.
新型的酯类香蕉型(弯曲形状)单体,1,3-亚苯基双[4'-(烯-1-氧基)-联苯-4-羧酸酯] Ia–Vb,具有不同取代基在中心苯环上(H、CH3、Cl 或 NO2)和侧臂上的烯基尾(癸烯基或十一烯基),已被制备。具有4-氯或4,6-二氯取代基的类似物 IIIa–IVb 显示出向列相,而具有2-硝基取代基的 Va,Vb 在相对较低的温度下显示出B7相。所有化合物都稳定,未观察到在应用的电场或热处理下发生降解或聚合。在每个样品的向列相中观察到电-流体动力学不稳定性。在Vb的B7相中,在112–114.5 °C范围内存在电光开关,在20 V µm−1场的开关时间约为150 µs。在较低温度下没有电光开关发生,但可以检测到铁电型自发极化22 nC cm−2。通过半经验的CAChe/MOPAC/PM5方法计算弯曲角度。