Symmetric bent-core mesogens with m-carborane and adamantane as the central units

Abstract

Several members of two homologous series of symmetric bent-shaped compounds with either m-carborane or adamantane (1[n] or 2[n], n = 9–13) in the central position were synthesized and investigated by optical, calorimetric, X-ray diffraction, and electro-optical methods. Results show that the two shortest members of the m-carborane series, 1[9] and 1[10], exhibit an intercalated lamellar B6 phase. The adamantane derivatives 2[9]–2[13] display a monotropic weakly birefringent soft crystalline or crystalline phase with homochiral domains. Neither phase undergoes polarization switching in an electric field.