Similarities and differences between molecular order in the nematic and twist-bend nematic phases of a symmetric liquid crystal dimer
| Autor: | Henry Joy, J. W. Emsley, Georg H. Mehl, Moreno Lelli, Maria-Gabriela Tamba |
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| Rok vydání: | 2016 |
| Předmět: |
Biaxial nematic
Condensed matter physics Chemistry Bent molecular geometry General Physics and Astronomy 02 engineering and technology Nuclear magnetic resonance spectroscopy 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences 0104 chemical sciences Magnetic field Condensed Matter::Soft Condensed Matter Crystallography Liquid crystal Molecule Physical and Theoretical Chemistry Twist 0210 nano-technology Anisotropy |
| Zdroj: | Physical chemistry chemical physics : PCCP. 18(14) |
| ISSN: | 1463-9084 |
| Popis: | The order parameter, Szz, where z is the para axis of the difluoroterphenyl groups in DTC5C9, has been obtained from chemical shift anisotropies measured by (13)C - {(1)H} NMR experiments at temperatures throughout the nematic, NU, and twist-bend nematic, NTB, phases shown by this compound. The order parameter temperature profiles are unusual in having a maximum value in the NU phase and then decreasing until the NTB phase is reached. There is a small discontinuity (∼2%) in Szz at TNNTB and then a gradual decrease until a new phase appears. This behaviour is interpreted as revealing a temperature-dependent tilting of local directors in both phases away from the applied magnetic field direction. In the enantiomorphic twist-bend phase this tilt is consistent with the structure of the phase as a helical arrangement of local directors, whilst in the high-temperature non-chiral nematic the tilt must involve a non-chiral arrangement. It is proposed that in both phases the tilting of directors has a common origin in the bent shape of the molecules. |
| Databáze: | OpenAIRE |
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