Experimental and Computational Study of a Liquid Crystalline Dimesogen Exhibiting Nematic, Twist-Bend Nematic, Intercalated Smectic, and Soft Crystalline Mesophases.

Liquid crystalline dimers and dimesogens have attracted significant attention due to their tendency to exhibit twist-bend modulated nematic (N) phases. While the features that give rise to N phase formation are now somewhat understood, a comparable structure-property relationship governing the formation of layered (smectic) phases from the N phase is absent. In this present work, we find that by selecting mesogenic units with differing polarities and aspect ratios and selecting an appropriately bent central spacer we obtain a material that exhibits both N and intercalated smectic phases.

Molecular shape as a means to control the incidence of the nanostructured twist bend phase.

Liquid crystalline phases with a spontaneous twist-bend modulation are most commonly observed for dimers and bimesogens with nonamethylene spacers. In order to redress this balance we devised a simple chemical intermediate that can be used to prepare unsymmetrical bimesogens; as a proof of concept we prepared and studied eleven novel materials with all found to exhibit the twist-bend phase and exhibit a linear relationship between TN-I and TTB-N. A computational study of the conformational landscape reveals the octamethyleneoxy spacer to have a broader distribution of bend-angles than the nonamethylene equivalent, leading to reductions in the thermal stability of the TB phase.