λ-Shaped azomesogens with polar chloro- and nitro-substituents

Abstract

A new homologous series of l-shaped mesogenic azo esters with polar chloro-and nitro-substituents has been synthesised by attaching a rigid 2-chloro-4-nitrophenylazo group to a resorcinol moiety by a central azo linkage. Both phenolic hydroxyl groups are esterified by 4-n-alkoxybenzoyl groups. All the compounds synthesised have been characterised using a combination of elemental analysis and standard spectroscopic methods. The mesomorphic properties of the compounds have been determined by polarising optical microscopy and differential scanning calorimetry. The lower members of the series are non-mesogenic, the middle members exhibit a nematic mesophase, and higher members exhibit a smectic A mesophase. The effect of polar chloro-, nitro-, and long lateral aromatic substituents, on mesomorphism is discussed.

Azoester-based H-shaped symmetrical mesogenic dimers containing – CH3/–OCH3terminal substituent

“…Shorter tails tend to make the compounds monotropically nematic, while longer tails produce smectic phases enantiotropically. Earlier we [14][15][16] reported on -shaped mesogenic homologous series and studied the dielectric, ferroelectric and polarization measurement. We [17] have also synthesized H-shaped azobenzene dimer molecule, bis[5-(4 0 -n-dodecyloxybenzoyloxy)-2-(4 00 -methylphenylazo)phenyl]adipate, and studied its monolayer film properties at air-water interfaces (Langmuir film) and air-solid interface (Langmuir-Blodgett film).…”