de Gennes' triclinic smectics – not so far-fetched after all

Abstract

Study of the optical symmetry of the high-temperature liquid crystal phase of the bent core molecule NORABOW produces the first direct evidence for a material having fluid layers with internally stabilised triclinic symmetry, exhibiting the SmCPG structure: spontaneous in-plane polar ordering as well as substantial coherent molecular tilt in two Euler angles, giving an optical dielectric tensor with none of the principal axes oriented in or normal to the layer plane. The resulting C₁ symmetry makes NORABOW layers the least symmetric fluids. This triclinic layer structure is found to be robust, depending little on the relative state of neighbouring layers or position relative to the air interface.

Keywords:

• liquid crystal
• bent-core
• triclinic

Acknowledgements

This work was supported by NSF Materials Research Science and Engineering Center Grant DMR 0820579, NASA grant NAG3–2457, and NSF Grant DMR 0606528.