Novel T-shaped Chiral Oligomers with a Wide Temperature Range of a Blue Phase

Abstract

The crystal structure of (S)-1-methylheptyl-4′-{4-octyloxy-2-{11-[4-(5-hexylpyrimidin-2-yl)phenoxy]undecanoyloxy}benzoyloxy}biphenyl-4-carboxylate, which has a relatively wide temperature range of blue phase III on cooling, has been determined. The molecule was found to form a λ-shaped structure. We have prepared a homologous series of the chiral oligomers and investigated effects of structure on appearance of the blue phase. All compounds were found to show a phase sequence of Iso-BP-N*-glass on cooling. The structure-property correlations reveal that (1) chirality does not affect on the Iso-BP transition temperature, (2) increasing chirality destabilizes the N* phase, and (3) the longer spacer lowers the BP-N* transition temperature.

Keywords:

• blue phase
• chirality
• liquid crystal
• molecular biaxiality

Notes

^a The melting points and glass transition temperatures were measured by DSC.

^b Enthalpies of the BP to N* transition were too small to be detected.

^a Helical pitch (µm) in the N* phase for a chiral nematic mixture of 6CB and 2 wt% of each chiral compound and that in the SmC* phase for a chiral mixture of 8-PYP-6O and 2 wt% of each chiral compound were observed at room temperature.

This work was partially supported by Aomori Prefecture Collaboration of Regional Entities for the Advancement of Technological Excellence, JST and a Grant for priority Research Designated by the President of Hirosaki University.