General Papers ARKIVOC 2008 (xvii) 157-166 Synthesis of liquid crystals materials derived from oxadiazole, isoxazole and tetrazole heterocycles Daniela Rubia dos Santos, a Ana Gabriela Silva de Oliveira, a Rafael Levi Coelho, a Iêda Maria Begnini, a Rachel Faverzani Magnago, b and Luciano da Silva c a Departamento de Química, Universidade Regional de Blumenau, 89012-900,Blumenau -SC, Brasil b Laboratório de Química das Engenharias – UnidadeTecnológica, Universidade do Sul de Santa Catarina, 88704-900, Tubarão - SC, Brasil c Laboratório de Pesquisa em Energia – Universidade do Vale do Itajaí, 88122-000, São José - SC, Brasil E-mail: luciano.silva@univali.br Abstract The synthesis is described of new liquid crystalline heteroaromatic compounds containing the five- membered isoxazole, tetrazole and 1,2,4-oxadiazole rings. Two liquid crystalline series including five- membered heterocycles were synthesized. The compounds with the mesogenic units tetrazole and isoxazole (Series I) showed nematic and smectic C phases, while the compounds with the units tetrazole and 1,2,4-oxadiazole (Series II) presented nematic (N), smectic C (Sm C ), and smectic A (Sm A ) mesophases. The transition temperatures and textures of the mesophases determined were characterized using polarized optical microscopy. Keywords: Liquid crystals, oxadiazole, isoxazole, tetrazole Introduction The design of novel thermotropic liquid crystals as advanced functional materials involves selection of a suitable core fragment, linking group, and terminal functionality. However, anisometric rod-like or disk-like molecules used to be a fundamental prerequisite for conventional thermotropic liquid crystal formation, because steric packing considerations play an important role in this interesting state of soft matter. 1-3 Over many years a large number of liquid-crystalline compounds containing heterocyclic units has been synthesized. 4-6 This research field has grown even more in recent years because of improvements in synthetic methodologies. Heterocycles are of great importance as core units in thermotropic liquid crystals owing to their ISSN 1551-7012 Page 157  ARKAT USA, Inc.