Twist-bend nematic liquid crystals based on thioether linkage

We developed twist-bend nematogens based on cyanobiphenyl dimers with thioether or sulfur linkage, as opposed to the commonly used methylene and ether linkages. Based on the smaller bond angle of thioether C-S-C than methylene C-CH2-C and ether C-O-C, we designed two dimer homologous series that are more bent, symmetric CBSnSCB with two thioether linkages and asymmetric CBSnOCB with a thioether and an ether linkage, containing odd carbon numbers n = 3, 5, 7, 9, and 11, and also synthesized even-n members n = 6 for each system. Both CBSnSCB with n = 3, 5 and 7 and CBSnOCB with n = 5 and 7 formed a broad range of twist-bend nematic (N-TB) phases that were stable down to room temperature and showed remarkably enhanced glass-forming ability. In addition, CBS9OCB also formed N-TB phase at a fast scan rate. DFT calculations revealed that twist-bend nematogens CBS7SCB and CBS7OCB have smaller bend angles made of the para axes of the two cyanobiphenyl moieties and larger dipole moments than those of the conventional nematogen ether-linked CBO7OCB.