Abstract
A series of azo-bridged benzothiazole-phenyl ethers 4-((6-ethoxybenzothiazol-2-yl)diazenyl)bromoalkoxybenzene in which an exocyclic N˭N group is situated between an ethoxy-substituted benzothiazole and a bromoalkoxyphenyl have been synthesized and characterized. The phase transition behavior of these compounds have been correlated against the variation of the flexible alkyl chain with n methylene units (CH2), ranging from 5 to 12. The thermal stability as reflected by the transition temperature range of the present homologues is found to be strongly dependent on the length of the CH2 units. All the members of this series exhibit enantiotropic nematic phases. However, upon further cooling, the compounds with n = 9–12 also behave as smectogens.
Acknowledgment
The main author (G-Y. Yeap) would like to thank Universiti Sains Malaysia for funding the project through an FRGS (Fundamental Research Grant Scheme) grant (account no. 203/PKIMIA/6711192).