The inverse phase sequence SmA-SmC in symmetric dimeric liquid crystals

Seven homologous symmetric dimeric liquid crystals are presented where two three-ring mesogenic units are connected by a bis(carbonyloxy) alkylene spa cer. For homologues with terminal heptyloxy, octyloxy and nonyloxy chains, the unusual phase sequence SmA-SmC with increasing temperature was detected by the study of the optical textures and by X-ray diffraction measurements . This unusual behaviour is discussed on the basis of the molecular structu re of these compounds.