Ferroelectric liquid crystal induced by a bridged biphenyl dopant with helical topography
作者:Carmen Lazar、Kexin Yang、Matthew A. Glaser、Michael D. Wand、Robert P. Lemieux
DOI:10.1039/b107435k
日期:2002.2.22
A new atropisomeric dopant containing a bridged biphenyl core with helical topography, 3,9-bis[(4-nonyloxy)benzoyloxy]-5,7-dihydro-1,11-dinitrodibenz[c,e]thiepin (2), was synthesized in optically pure form and doped in the liquid crystal host 2-(4-butyloxyphenyl)-5-octyloxypyrimidine (PhP1) to produce a ferroelectric SmC* phase. The polarization power δp of this new dopant is compared to that of an analogous unbridged dopant, 2,2′-dimethyl-6,6′-dinitro-4,4′-bis[(4-n-nonyloxy)benzoyloxy]biphenyl (1), after normalizing for a difference in core transverse dipole moments. Results show that the normalized polarization power of the bridged dopant 2 is greater than that of the unbridged dopant 1 by a factor of 5.3. On the other hand, the SmC* helical pitch p induced by 2 is shorter than that induced by 1 by a factor of 1/6.7. This inverse relationship is consistent with predictions that dopant 2 should have a greater propensity to undergo chirality transfer with surrounding host molecules via conformational core–core interactions. A more direct assessment of the chiral perturbation exerted on the host molecules is achieved by studying the effects of dopants 1 and 2 on the spontaneous polarization induced by a probe chiral dopant, (S,S)-5-(2,3-difluorooctyl)-2-(4-octylphenyl)pyridine (MDW950), which mimics the structure of PhP1.
研究人员合成了一种新的异构体掺杂剂--3,9-双[(4-壬氧基)苯甲酰氧基]-5,7-二氢-1,11-二硝基二苯并[c,e]硫杂卓(2),这种掺杂剂含有一个具有螺旋拓扑结构的桥联联苯核,并掺入液晶宿主 2-(4-丁酰氧基苯基)-5-辛酰氧基嘧啶(PhP1)中以产生铁电性 SmC* 相。在对核心横向偶极矩的差异进行归一化处理后,将这种新掺杂剂的极化功率δp 与类似的无桥掺杂剂 2,2′-二甲基-6,6′-二硝基-4,4′-双[(4-壬酰氧基)苯甲酰氧基]联苯 (1) 的极化功率δp 进行了比较。结果表明,桥接掺杂剂 2 的归一化极化功率比未桥接掺杂剂 1 大 5.3 倍。另一方面,2 诱导的 SmC* 螺旋间距 p 比 1 诱导的短 1/6.7。这种反比关系与掺杂剂 2 通过构象核心-核心相互作用与周围宿主分子发生手性转移的倾向更大的预测相一致。通过研究掺杂剂 1 和 2 对探针手性掺杂剂--(S,S)-5-(2,3-二氟辛基)-2-(4-辛基苯基)吡啶 (MDW950)--诱导的自发极化的影响,可以更直接地评估对宿主分子施加的手性扰动。