Synthesis and thermal properties of liquid crystalline compounds containing carbazolyl group

New liquid crystalline compounds containing carbazolyl moiety as part of th e mesogenic group were synthesized. 2-(9-Methylcarbazolyl)-4-alkoxybenzoate and 2-(9-methylcarbazolyl)-4-trifluoromethylbenzoate did not show any text ures by polarizing optical microscopy (POM) measurement. However, 2-(9-meth ylcarbazolyl)-4-cyanobenzoate and 2-(9-metylcarbazolyl)-4-alkanecarboxybenz oate ate show schlieren texture. 2-(9-methylcarbazolyl)-4-cyanobenzoate has two phase transition temperatures on both heating and cooling process. By X-ray diffraction Measurement of this compound, only one weak broad peak wa s detected at the mesomorphic temperature in the wide-angle region. Therefo re, the LC phase of the compound wag assigned to a nematic. 2-(9-Methylcarb azolyl)-4-pentynylcarboxybenzoate shows only one phase transition on heatin g process. However, the compound shows two phase transition temperatures on cooling processes. By X-ray diffraction measurement, the compound indicate s two broad peaks at around 4.5 and 19.0 degree. These LC phases would be a ssigned to a cybotactic nematic phase based on the shorten molecular length of the calculated value and the optical texture.