Mesophase properties of fluorene-core mesogens and their effects on blue phase liquid crystals

ABSTRACT

Two series of fluorene-core compounds were successfully synthesised, one series of compounds have different rigid conjugated structures, and the other series of compounds have different substituted dialkyl chains at the 9-position of fluorene core. The thermotropic mesomorphic behaviours and fluorescence characteristics of the synthesised compounds were investigated. It was found that these derivatives exhibited well fluorescence performance and wide mesophases range up to 196°C. The short dialkyl chains substituted at the fluorenyl 9-position can improve the solubility of the compounds while maintaining the mesogenic properties. It was also found that the fluorene-derived compounds as dopants of chiral nematic liquid crystal can effectively stabilise the double-twisted structure due to the biaxiality of fluorene core, so as to induce the emergence of blue phase or broaden its temperature range.

Graphical abstract

KEYWORDS:

• Fluorene
• bent-shaped compounds
• blue phase
• mesogenic properties

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the National Key R&D Program of China [2018YFB0703703], the National Natural Science Foundation of China [61370048, 51673023, 51773017, 51973017], the State Key Laboratory for Advanced Metals and Materials [2018Z-06] and the Fundamental Research Funds for the Central Universities [FRF-DF-19-001]. The authors also thank Prof. Meiju Wei from University of Science and Technology Beijing for the molecular simulation in this work.