The Chiral Twist-Bend Nematic Phase (N*TB)

The twist-bend nematic, NTB, 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, NTB, is completely miscible with the NTB phase of the standard achiral material, CB6OCB. The NTB phase exhibits optical textures with lower birefringence than those observed for the achiral NTB phase, suggesting an additional mechanism of averaging molecular orientations. The N*@NTB transition temperatures for the chiral materials are higher than the NTB @N transition temperatures seen for the corresponding racemic materials. This suggests the double egeneracy of helical twist sense in the N TB 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*TB–N phase transition, which may be attributed to a non-monotonic dependence of the bend elastic constant.