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

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. [ABSTRACT FROM AUTHOR]