Synthesis and characterisation of thieno[3,2-b]thiophene-based linear shaped liquid crystals

Abstract

A series of thieno[3,2-b]thiophene-based liquid crystalline molecules has been synthesised. To investigate the effects of alkyl substituent groups and structure of mesogenic cores, eight kinds of thieno[3,2-b]thiophene-based molecules containing different alkyl substituent groups and mesogenic cores have been synthesised. These molecules were characterised by differential scanning calorimetry, polarising optical microscopy, ultraviolet–visible absorption spectroscopy, fluorescence spectroscopy, cyclic voltammetry and polarised fluorescence spectroscopy. The results indicated that the thieno[3,2-b]thiophene-based donor-acceptor-donor (D-A-D) type molecules showed the presence of a smectic A phase. Changes in the length of alkyl substituents and mesogenic cores affected the phase transitions, optical and electrochemical properties of the molecules.

Keywords:

• thieno[3,2-b]thiophene
• linear shaped liquid crystal
• donor-acceptor-donor structure

Acknowledgements

We would like to thank the OPEN FACILITY, Research Facility Center for Science and Technology, University of Tsukuba, for allowing us to use nuclear magnetic resonance spectrometer, fluorospectro photometer and differential scanning calorimetry measurements. We would like to sincerely acknowledge and thank Hirotsugu Kawashima, Kazuho Ishise, Tomokazu Iseki and Aohan Wang for their help and support.