Non-Symmetric Liquid Crystal Dimers: High Thermal Stability in Nematic Phase Enhanced by Thiophene-2-Carboxylate Moiety

Abstract

Series of non-symmetric liquid crystal dimers, α-(4-benzylidenechloroaniline-4′-oxy)-ω-[4-(thiophene-2-carboxyl)benzylideneaniline-4′-oxy]alkanes incorporating a thiophene-based moiety in one of the two mesogenic units have been synthesized and characterized. The nematogenic properties of the dimers were studied wherein the flexible spacers made up by n methylene units (–CH₂-) ranging from n=5 to n=12. These dimers exhibit enantiotropic N phase with high thermal stability (>187.0°C). The N phase temperature range for the present homologues is found to be strongly dependent on the length and parity of the methylene spacer which connects the 4-benzylidenechloroaniline and 4-(thiophene-2-carboxyl)- benzylideneaniline mesogenic cores.

Keywords:

• enantiotropic N phase
• high thermal stability
• non-symmetric liquid crystal dimers
• thiophene

ACKNOWLEDGMENTS

The main author (G.-Y. Yeap) acknowledges the Malaysian Ministry of Science, Technology and Innovation (MOSTI) for the research grant (eScience No.03–01-05-SF0366 or 305/PKIMIA/613328). The authors thank Professor Corrie T. Imrie (University of Aberdeen, Scotland) and Professor Ewa Gorecka (Warsaw University, Poland) for some helpful comments.