New azobenzene containing bent-core liquid crystals based on disubstituted resorcinol

Abstract

New bent-core molecules with 4,6-dichlororesorcinol or 4-chloro-2-methylresorcinol as the central unit, and azobenzene with different alkyloxy chain length as side arms were synthesised. The mesophase behaviour of the new compounds was investigated by polarising optical microscopy, differential scanning calorimetry, X-ray diffraction studies and electro-optical measurements. It is found that 4,6-dichlororesorcinol is more conducive towards mesomorphism than 4-chloro-2-methylresorcinol. The liquid crystalline properties of all of the prepared compounds are greatly affected by the lateral substitution on the outer ring. 4,6-Dichlororesorcinol-based compounds without lateral substitution show nematic phases with cybotactic cluster of the SmC-type (N_CybC). Moreover, depending on the chain length, the nematic phase appears as enantiotropic phase for the shortest homologue and as monotropic phase for the higher homologues.

Keywords:

• bent-core liquid crystals (BCLCs)
• azobenzene
• 4,6-dichlororesorcinol
• 4-chloro-2-methylresorcinol
• nematic phase

Acknowledgements

M. Alaasar is grateful to the Alexander von Humboldt Foundation for the research fellowship at Martin-Luther University, Halle, Germany.