Issue 32, 2017

Oriented columnar films of a polar 1,2,3-triazole-based liquid crystal prepared by applying an electric field

Abstract

We report the electric-field (E-field)-assisted orientation of a bent-core liquid crystal (LC) based on the polar 1,2,3-triazolyl group. The LC exhibited a hexagonal columnar (COLhex) phase at ambient temperature, which transformed into a disordered columnar (COLdis) phase with short-range correlation upon heating. Dielectric relaxation spectroscopy and switching studies revealed that the aromatic cores could undergo in-plane rotation (α-relaxation) in the COLhex phase, while R-relaxation allowing the reorientation of the triazolyl units along the E-field direction occurred in the COLdis phase. Infrared spectroscopy confirmed that the hydrogen-bonding interactions between triazolyl units along the columnar axis affected the molecular motion. Based on the dynamics studies, two columnar alignment methods under E-fields, i.e., an isothermal method in the COLhex phase and a cooling method from the COLdis to COLhex phase were examined. Both methods give high-quality oriented columnar thin films. In particular, the cooling method requires less time (only 1 min) and a weaker E-field (10 V μm−1), and therefore, it could be applied to the alignment of a bulk-level film (thickness: 260 μm). The successful orientation could be verified by in situ X-ray diffraction analysis under an E-field. The current–voltage curves before and after the alignment indicated that the orientation process enhanced electric conduction.

Graphical abstract: Oriented columnar films of a polar 1,2,3-triazole-based liquid crystal prepared by applying an electric field

Supplementary files

Article information

Article type
Paper
Submitted
17 Jun 2017
Accepted
24 Jul 2017
First published
25 Jul 2017

J. Mater. Chem. C, 2017,5, 8256-8265

Oriented columnar films of a polar 1,2,3-triazole-based liquid crystal prepared by applying an electric field

M. L. Nguyen, T. J. Shin, H. Kim and B. Cho, J. Mater. Chem. C, 2017, 5, 8256 DOI: 10.1039/C7TC02710A

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