Smectic-like batonnets in nematic/twist-bend nematic biphasic samples

We have studied a mixture of the twist-bend nemogenic dimer CB7CB with rod-like nematic molecules, which exhibits nematic (N) and twist-bend nematic (N-TB) phases and a very large biphasic coexistence range. At the N-N-TB transition, we observe the nucleation of highly anisometric N-TB droplets which are very similar to the classic smectic A (SmA) batonnets. These observations confirm the recently proposed close analogy between the N-TB and SmA phases, on the basis of their identical macroscopic symmetry. As for their smectic analogues, the N-TB batonnets are fluid in two dimensions; they easily merge when brought into contact and they are solid-like in that they did not flow along their optic axis. The observed fluidity and low viscosity show that the N-TB phase is indeed a nematic phase, i.e. an anisotropic fluid, rather than a soft crystal or glassy state. Unlike their smectic analogues, the N-TB batonnets have almost perfect symmetry of revolution and the axis of the N-TB helix is uniformly aligned parallel to the long axis of the batonnet. The large aspect ratio of the batonnets, typically = 10-30, indicates a very strong anisotropy of the N-N-TB interfacial energy, W-2/W-0 approximate to 200-2000, and suggests that the anchoring energy differs from the usual Rapini-Papoular form. [GRAPHICS] .