Optically Biaxial, Re-entrant and Frustrated Mesophases in Chiral, Non-symmetric Liquid Crystal Dimers and Binary Mixtures
作者:Vediappen Padmini、Palakurthy Nani Babu、Geetha G. Nair、D. S. Shankar Rao、Channabasaveshwar V. Yelamaggad
DOI:10.1002/asia.201600918
日期:2016.10.20
spacer, were synthesized and characterized. While the terminal chiral tail, in the form of either (R)‐2‐octyloxy or (S)‐2‐octyloxy chain attached to salicylaldimine core, was held constant, the number of methylene units in the spacer was varied from 3 to 10 affording eight pairs of (R & S) enantiomers. They were probed for their thermal properties with the aid of orthoscopy, conoscopy, differential scanning
合成并表征了十六种旋光性,非对称二聚体,其中氰基联苯和水杨醛亚胺的液晶元通过柔性间隔基相互连接。尽管末端手性尾巴(以(R)-2-辛氧基或(S)-2-辛氧基链形式连接至水杨醛亚胺核心)保持恒定,但间隔基中的亚甲基单元数从3变为10提供八对(R&S)对映异构体。借助矫形镜,锥形镜,差示扫描量热法和X射线粉末衍射对它们的热性能进行了探测。此外,使用手性和非手性二聚体进行了二元混合物研究,其目的是稳定光学双轴相/秒,折返相和重要的相序。值得注意的是,手性二聚体之一和某些混合物表现出双轴近晶A(SmA b)相出现在单轴SmA和折返单轴SmA相之间。在大多数二聚体和混合物中也发现了中间相,例如手性向列相(N *)和受挫相,即蓝相(BPs)和扭曲晶界(TGB)相。X射线衍射研究表明,具有氧丁氧基和氧戊氧基间隔基的二聚体显示出相互交叉的(SmA d)相,其中近晶周期性是分子长度的1.4倍以上。而在插值SmA(SmA