Rod-like liquid crystalline molecules with ring-fixed benzanilides

Rod-like liquid crystals (LCs) consist of a linear rigid core and flexible hydrocarbon chains, and the resulting LC properties are significantly affected by these chemical structures. In designing rod-like LCs, tertiary amides are rarely employed, owing to their stability in the cis conformation (bent shape), while secondary amides have been utilised because of their stability in the trans conformation (rod-like shape). In this study, we synthesised rod-like LCs incorporating ring-fixed benzanilides, in which the Ar-CO and amide bonds are fixed, denoted as PBA[n] (n = 5, 6, 7). Their properties were evaluated through polarised optical microscopy, differential scanning calorimetry, and wide-angle X-ray diffraction measurements. The findings indicate that the LC properties can be modulated by varying the ring size. Furthermore, single-crystal structural analysis revealed the molecular alignment potential enabled facilitated　by the ring-fixed benzanilide.