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, N*TB, is completely miscible with the NTB phase of the standard achiral material, CB6OCB. The N*TB 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*@N*TB 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.