Synthesis and characterisation of photopolymerisable liquid crystals based on the π-extended fluorene core and their corresponding non-reactive analogues

Abstract

We have synthesised a series of new reactive mesogens with photopolymerisable di-acrylates and their corresponding non-reactive analogues based on the π-conjugated aromatic core, fluorene (F)-di-[thiophene (T)-benzene (B)], using the Stille and Suzuki coupling reaction. The effect of lateral alkyl chains on the 9-position of the central fluorene moiety as well as α, ω- side alkyl chains attached to the π-conjugated aromatic core on the mesomorphism was investigated by utilising differential scanning calorimetry (DSC) and polarising optical microscopy (POM). A wide angle X-ray scattering (WAXS) study at the various temperatures was also carried out to reveal phase structures. Photopolymerisable di-acrylates connected directly to the rigid aromatic core showed higher phase transition temperatures, probably due to the induced dipole moment in comparison with those of a non-reactive methyl–ether counterpart.

Keywords:

• reactive mesogens
• fluorene
• phase transition
• mesomorphism
• photopolymerisable di-acrylate

Acknowledgements

This research was supported by a grant from the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy, Republic of Korea. We thank Dr. Se Hoon Gihm, Seoul National University, for help on WAXS interpretation. The authors also wish to thank Professor E-Joon Choi, Kumoh National Institute of Technology, for fruitful discussions. We are indebted to the referee for constructive and helpful comments.