The Dependency of Nematic and Twist-bend Mesophase Formation on Bend Angle.

We have prepared and studied a family of cyanobiphenyl dimers with varying linking groups with a view to exploring how molecular structure dictates the stability of the nematic and twist-bend nematic mesophases. Using molecular modelling and 1D H NOESY NMR spectroscopy, we determine the angle between the two aromatic core units for each dimer and find a strong dependency of the stability of both the nematic and twist-bend mesophases upon this angle, thereby satisfying earlier theoretical models.

Chiral dopants and the twist-bend nematic phase--induction of novel mesomorphic behaviour in an apolar bimesogen.

Herein we report studies on a bimesogen that exhibits a chiral twist bend nematic phase when doped with small weight percentages of a chiral material and a partial phase diagram constructed. At low concentrations a wide temperature range blue phase is observed, whereas at higher concentrations an additional 'nematic-like' mesophase was discovered at a lower temperature than the twist-bend nematic phase. In addition to an apparent isotropic-"isotropic" transition, the doped materials also exhibited a weakly birefringent phase upon annealing in the isotropic liquid phase, implying pretransitional behaviour in the same vein as that seen for TGB phases.

Apolar bimesogens and the incidence of the twist-bend nematic phase.

The nematic twist-bend phase (NTB) was, until recently, only observed for polar mesogenic dimers, trimers or bent-core compounds. In this article, we report a comprehensive study on novel apolar materials that also exhibit NTB phases. The NTB phase was observed for materials containing phenyl, cyclohexyl or bicyclooctyl rings in their rigid-core units.