Polar smectic phases in quasi-bent-core liquid crystals with hockey-stick-shaped mesogen: synthesis and crossover mesomorphism

Abstract

New hockey-stick-shaped liquid crystals (HSLCs) have been designed and synthesised. By extreme shortening of one 'arm' in the HSLCs, we have constructed the pronounced overall hockey-stick-shaped molecular conformation of these materials, and called the pseudo-rod-like (PRL) molecules with hockey-stick-shaped mesogen. The chemical structures were identified using spectroscopy and elemental analysis. The mesomorphic behaviour was investigated by polarising optical microscopy (POM), differential scanning calorimetry (DSC), X-ray diffractometry (XRD), and via electro-optical experiments. As a result, in spite of the PRL molecules, the various mesomorphic polymorphism, the interdigitated bi-layered structure and macroscopic polarity were found. Similar to up-to-date HSLCs, the quasi-bent-core LCs showed a transition from the synclinic SmC phase (SmCs) to anticlinic SmC (SmCa) phase, and exhibited SmA-type (N-CybA) and SmC-type (N-CybC) cybotactic nematic phases. At the same time, similar to practical rod-like LCs, the PRL molecules showed good surface alignment behaviour under planar boundary conditions.