The effect of a thiophene ring in the outer position on mesomorphic properties of the bent-shaped liquid crystals

Abstract

Novel bent-shaped compounds with the naphthalene central core possessing an outer thiophene unit in the lengthening arm were synthesized. Mesomorphic behaviour of new materials was studied using optical polarising microscopy, DSC, and electrooptic methods. The structures of mesophases were identified by X-ray diffraction and the structural parameters established. In the case of the thiophene unit in one molecular arm (the phenyl in the opposite arm) we succeeded in obtaining mesogenic properties for all types of lateral substitutions on the central naphthalene core. All non-substituted compounds and materials with the central core substituted by CH₃ or Cl exhibited the B₂ phase. The B₇ phase has been observed for all compounds with CN-substituted central core. Materials with the thiophene unit in both lengthening arms were not liquid crystalline except for the CN-substituted compound exhibiting the B₇ phase. Mesomorphic properties of compounds with the thiophene are compared with those detected on analogous materials with the phenyl ring.