On the supramolecular packing of bent-shaped molecules: the influence of the central bent-core on the liquid crystalline behaviour

Abstract

Two series of bent-shaped molecules have been synthesized and their supramolecular self-organization at variable temperature has been studied. The majority of these bent-compounds form liquid crystalline phases and the mesomorphic behaviour of them has been fully characterized by polarised optical microscopy, calorimetry, X-ray diffraction and dielectric techniques. A series of bis-4-n-tetradecyloxybenzoyloxybenzoates derived from naphthalene, resulting in a change of the bending angle, have proved that when these cores bend around 120°, a polar lamellar packing (SmC_aP_A) can be induced, whereas when the angle was around 60°, an orthogonal lamellar arrangement (SmA) that responded to an electric field, are found to occur. Liquid-crystal order can also be achieved over a significant range of temperatures by using appropriate bis-4,4′-disubstituted phenylene derivatives (–Ar–X–Ar–). Groups such as –CO–, SO– and –CH₂– connecting the aromatic rings induce the SmC_aP_A phase while a sulfide group (–S–) leads to columnar order. Further, the formation of isotropic textures as chiral conglomerates or a field-induced phase transition have also been observed as unusual properties of the self-organizations of these compounds.