Polar columnar and lamellar mesophases in homologous bent-core compounds derived from methyl 3,5-dihydroxybenzoate

Abstract

The synthesis and mesomorphic properties of the first three homologous series of symmetrical seven-ring bent-core compounds derived from methyl 3,5-dihydroxybenzoate have been described. In all the three series the lower homologues show an intercalated smectic (B₆) phase. The middle homologues exhibit a polar columnar phase that shows antiferroelectric characteristics, while the higher homologues exhibit a switchable smectic phase with chiral conglomerates (SmCP_AF). More interestingly, in one of the homologues, coexistence of a switchable columnar phase and a switchable lamellar phase has been observed. The mesophases were characterised using classical techniques of polarised light optical microscopy, differential scanning calorimetry, X-ray diffraction and electro-optical studies.

Keywords:

• lateral substituent
• polar columnar phase
• antiferroelectric
• SmCP_AF phase
• coexistence

Acknowledgements

The authors wish to thank Ms. K. N. Vasudha for technical support and the NMR Research Centre, Indian Institute of Science, Bangalore for recording the NMR spectra. BKS wishes to acknowledge the financial support given by the Indian National Science Academy, New Delhi.