Mesogenic Schiff's base ether with dimethylamino end group

Abstract

A series of Schiff base ethers comprising a dimethylamino group at one terminal position and an even number of carbons at the other along the molecular axis was studied. The dimethylamino unit, acting as a charge-transfer donor in the formation of conjugative interactions, contributes to the molecule's polarizability and in turn affecting its intermolecular interactions, leading to the formation of less-ordered mesophase. The mesomorphic properties were studied using polarizing optical microscopy and differential scanning calorimetry. Whilst the n-butyloxy to n-hexadecyloxy derivatives exhibited nematic phase, the n-ethyloxy, n-propyloxy and n-octadecyloxy derivatives were not mesogenic. Their phase transitions during heating and cooling run were presented. The title compounds were compared with other structurally related series to establish their chemical structure–mesomorphic property relationships.

Keywords:

• Schiff base
• p-n-(dimethylamino)benzylidene-p-alkyloxyanilines
• nematic
• structure–property relationships

Acknowledgements

S.T. Ha would like to thank Universiti Tunku Abdul Rahman (UTAR) for the financial support through UTAR Vote No. 6202/O05 and the Malaysia Toray Science Foundation (UTAR Vote No. 4359/000) for funding this project. L.K. Ong would like to acknowledge UTAR for the award of the research assistantship.