New cholesteryl-containing bent core liquid crystals

The paper presents the synthesis and mesomorphic behavior of two new series of bent core liquid crystalline compounds based on a 1,3-dihydroxybezene core and containing a cholesteryl 6-oxyhexanoate wing. The two series were obtained by esterification of the cholesteryl 6-(3-hydroxyphenoxy)hexanoate core with some 4-{[4-(n-alkyloxy)phenyliazo}benzoic acids (n-alkyl = n-hexyl - n-dodecyl) or 4-{[4-(n-alkyloxy)benzoylioxylbenzoic acids (n-alkyl = n-hexyl - n-decyl). The esterification reactions were performed via the corresponding acyl chlorides or with the dicyclohexylcarbodiimide/4-(N,N-dimethylamino)pyridine (DCC/DMAP) system. All the synthesized compounds evidenced enantiotropic liquid crystalline properties with smectic type textures when investigated by differential scanning calorimetry and polarized optical microscopy. Isotropization and isotropic to liquid crystal transitions occurred at relatively low temperatures (between 89 and 146 degrees C). The compounds containing the azo-aromatic linking group presented the largest range of stability of the mesophases (between 42 and 87 degrees C). All the investigated compounds were thermally stable in the range of the existence of mesophases.