Anomalous temperature dependence of layer spacing of de Vries liquid crystals: Compensation model

Journal Article · Mon Jun 13 04:00:00 EDT 2016 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4953598· OSTI ID:22590802

Merkel, K. ^[1]; Kocot, A. ^[2]; Stevenson, P. J.; Panov, A.; Rodriguez, D. ^[3]

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1. Central Mining Institute, Katowice 40-166 (Poland)
2. Institute of Physics, Silesian University, Katowice 40-007 (Poland)
3. School of Chemistry and Chemical Engineering, Queens University Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom)

Smectic liquid crystals that exhibit temperature independent layer thickness offer technological advantages for their use in displays and photonic devices. The dependence of the layer spacing in SmA and SmC phases of de Vries liquid crystals is found to exhibit distinct features. On entering the SmC phase, the layer thickness initially decreases below SmA to SmC (T{sub A–C}) transition temperature but increases anomalously with reducing temperature despite the molecular tilt increasing. This anomalous observation is being explained quantitatively. Results of IR spectroscopy show that layer shrinkage is caused by tilt of the mesogen's rigid core, whereas the expansion is caused by the chains getting more ordered with reducing temperature. This mutual compensation arising from molecular fragments contributing to the layer thickness differs from the previous models. The orientational order parameter of the rigid core of the mesogen provides direct evidence for de Vries cone model in the SmA phase for the two compounds investigated.

• OSTI ID: 22590802
• Journal Information: Applied Physics Letters, Journal Name: Applied Physics Letters Journal Issue: 24 Vol. 108; ISSN APPLAB; ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
INFRARED SPECTRA
LAYERS
LIQUID CRYSTALS
ORDER PARAMETERS
SHRINKAGE
TEMPERATURE DEPENDENCE
THICKNESS
TRANSITION TEMPERATURE