Constitutional bis(N-salicylideneaniline)s as new class of mesogens: synthesis and thermal properties

Abstract

Twelve new constitutional bis(N-salicylideneaniline)s (BSANs) belonging to three different series have been prepared and characterised by the two-fold reaction of alkoxyanilines with 2,3-dihydroxyterephthalaldehyde, 4,6-dihydroxyisophthalaldehyde and 2,5-dihydroxyterephthalaldehyde. Their thermal behaviour and liquid crystallinity has been established with the help of polarising optical microscope, differential scanning calorimeter (DSC) and powder X-ray diffraction (XRD). Our study reveals this behaviour as determined by the nature of central core and the number of alkoxy tails. For example, the three series of compounds prepared are either non-mesomorphic or stabilised calamitic and discotic mesophases, such as nematic/smectic C and columnar (Col) phases. These materials represent the first examples of mesogenic BSANs exhibiting mesomorphism.

Keywords:

• bis(N-salicylideneaniline)s
• discotics
• calamitics
• nematic phase
• smectic C phase
• columnar phase

Acknowledgements

The author sincerely thanks Dr D.S. Shankar Rao for providing XRD data and helpful discussions. She also expresses her gratitude to Dr Praveer Asthana, Prof. K.A. Suresh and Dr Geetha G. Nair (mentor of the project) for their support and encouragement.