Issue 3, 2020

Frustration between two- and three-dimensional smectic ordering leads to a biaxial nematic phase

Abstract

The bola-amphiphilic, T-shaped mesogen CT2 has an aromatic, biphenyl core terminated on both ends by hydrophilic groups and a semi-perfluorinated, aliphatic side chain. Upon cooling from the isotropic phase, the fluorinated tails and the polar, rod-like cores nanophase-segregate to form a fluid lamellar phase. At high temperatures, the biphenyl cores are orientationally disordered in two dimensions (2D) in the lamellar planes but on further cooling the cores order orientationally, giving a biaxial lamellar phase with 2D nematic in-plane ordering. At lower temperature, the aromatic and hydrophilic parts of the cores nanosegregate within the lamellae and 2D smectic correlations of the head groups develop. X-ray diffraction shows that this 2D smectic ordering is incompatible with the initial lamellar structure, with both structures becoming short-ranged, resulting in a 3D biaxial nematic phase with macroscopic orthorhombic symmetry featuring strong smectic correlations in two orthogonal spatial dimensions. Freeze-fracture transmission electron microscopy enables direct visualization of the resulting short-ranged periodic structures.

Graphical abstract: Frustration between two- and three-dimensional smectic ordering leads to a biaxial nematic phase

Supplementary files

Article information

Article type
Paper
Submitted
07 Sep 2019
Accepted
26 Nov 2019
First published
11 Dec 2019

Soft Matter, 2020,16, 747-753

Author version available

Frustration between two- and three-dimensional smectic ordering leads to a biaxial nematic phase

D. Chen, D. A. Coleman, C. Zhu, N. Chattham, F. Jenz, X. Cheng, C. Tschierske, M. A. Glaser, J. E. Maclennan and N. A. Clark, Soft Matter, 2020, 16, 747 DOI: 10.1039/C9SM01809C

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