Department of Chemistry, School of Natural and Computing Sciences, University of Aberdeen, Meston Building, Aberdeen, AB24 3UE, UK.
Faculty of Chemistry, University of Warsaw, ul. Zwirki i Wigury 101, 02-089, Warsaw, Poland.
Chemistry. 2019 Oct 17;25(58):13329-13335. doi: 10.1002/chem.201903014. Epub 2019 Sep 5.
The twist-bend nematic, N , phase has been observed for chiral materials in which chirality is introduced through a branched 2-methylbutyl terminal tail. The chiral twist-bend nematic phase, N* , is completely miscible with the N phase of the standard achiral material, CB6OCB. The N* phase exhibits optical textures with lower birefringence than those observed for the achiral N phase, suggesting an additional mechanism of averaging molecular orientations. The N*-N* transition temperatures for the chiral materials are higher than the N -N transition temperatures seen for the corresponding racemic materials. This suggests the double degeneracy of helical twist sense in the phase is removed by the intrinsic molecular chirality. A square lattice pattern is observed in the N* phase over a temperature range of several degrees above the N* -N phase transition, which may be attributed to a non-monotonic dependence of the bend elastic constant.
扭曲向列相 N 已经在通过支化 2-甲基丁基末端尾链引入手性的手性材料中被观察到。手性扭曲向列相 N与标准非手性材料 CB6OCB 的 N 相完全混溶。N相表现出比非手性 N 相更低双折射的光学织构，这表明存在一种分子取向平均的附加机制。手性材料的 N*-N转变温度高于相应外消旋材料的 N-N 转变温度。这表明在 N 相中螺旋扭曲感的双重简并被分子手性所消除。在 N-N 相转变温度以上几度的温度范围内，在 N*相中观察到一个正方形晶格图案，这可能归因于弯曲弹性常数的非单调依赖性。
