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

Abstract

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. This result indicates that a tight distribution of bend-angles should stabilise the TB phase and lead to direct TB-Iso phase transitions, and conversely a broader distribution should destabilise the TB phase which may allow new states of matter that are occluded by the incidence of this phase to be revealed.