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 <i>cis</i> conformation (bent shape), while secondary amides have been utilised because of their stability in the <i>trans</i> 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 <b>PBA[<i>n</i>]</b> (<i>n</i> = 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.