Unusual smectic phases organized by novel λ-shaped mesogenic molecules

A homologous series of novel lambda-shaped mesogenic compounds in which three mesogenic groups are connected to 3, 4-dihydroxybenzoic acid has been prepared and their physical properties investigated by means of optical microscopy, differential scanning calorimetry and X-ray diffraction measurements. The lambda-shaped compounds studied showed unusual smectic phases. 4-Cyanobiphenyl-4'-yl 3,4-bis{6-[4-(5-octylpyrimidin-2-yl)phenyloxy]hexyloxy} benzoate was found to realize an incommensurate SmA (SmAinc) phase. A "uniform planarly" aligned sample of 2-(4-octylphenyl)pyrimidin-5-yl 3,4-bis{6-[4-(5-octylpyrimidin-2-yl)phenyloxy]hexyloxy} benzoate showed a Schlieren-like texture in the smectic phase. We discuss structural effects of the lambda-shaped compounds on molecular organization in liquid-crystal line phases.