Understanding the twist-bend nematic phase: the characterisation of 1-(4-cyanobiphenyl-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OCB) and comparison with CB7CB

Daniel A Paterson, Min Gao, Young-Ki Kim, Afsoon Jamali, Kirsten Finley, Beatriz Robles-Hernandez, Sergio Diez-Berat, Josep Salud, M. Rosario de la Fuente, Bakir A. Timimi, Herbert Zimmermann, Cristina Greco, Alberta Ferrarini, John M. D. Storey, David Orencio Lopez, Oleg D. Lavrentovich, Geoffrey R. Luckhurst, Corrie T Imrie

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Abstract

The synthesis and characterisation of the nonsymmetric liquid crystal dimer, 1-(4-cyanobiphenyl-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OCB) is reported. An enantiotropic nematic (N)-twist-bend nematic (NTB) phase transition is observed at 109˚C and a nematic-isotropic phase transition at 153˚C. The NTB phase assignment has been confirmed using polarised light microscopy, freeze fracture transmission electron microscopy (FFTEM), 2H-NMR spectroscopy, and X-ray diffraction. The effective molecular length in both the NTB and N phases indicates a locally intercalated arrangement of the molecules, and the helicoidal pitch length in the NTB phase is estimated to be 8.9 nm. The surface anchoring properties of CB6OCB on a number of aligning layers is reported. A Landau model is applied to describe high-resolution heat capacity measurements in the vicinity of the NTB-N phase transition. Both the theory and heat capacity measurements agree with a very weak first-order phase transition. A complementary extended molecular field theory was found to be in suggestive accord with the 2H-NMR studies of CB6OCB-d2, and those already known for CB7CB-d4. These include the reduced transition temperature, TNTBN/TNI, the order parameter of the mesogenic arms in the N phase close to the NTB-N transition, and the order parameter with respect to the helix axis which is related to the conical angle for the NTB phase.
Original languageEnglish
Pages (from-to)6827-6840
Number of pages14
JournalSoft matter
Volume12
Issue number32
Early online date11 Jul 2016
DOIs
Publication statusPublished - 2016

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Hexanes
Phase transitions
Specific heat
Liquid Crystals
specific heat
Light polarization
nuclear magnetic resonance
Dimers
Nuclear magnetic resonance spectroscopy
Optical microscopy
Surface properties
helices
polarized light
surface properties
Nuclear magnetic resonance
Transmission electron microscopy
X ray diffraction
Molecules
transition temperature
liquid crystals

ASJC Scopus subject areas

  • Chemistry(all)
  • Condensed Matter Physics

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Understanding the twist-bend nematic phase: the characterisation of 1-(4-cyanobiphenyl-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OCB) and comparison with CB7CB. / Paterson, Daniel A; Gao, Min; Kim, Young-Ki; Jamali, Afsoon; Finley, Kirsten; Robles-Hernandez, Beatriz; Diez-Berat, Sergio; Salud, Josep; de la Fuente, M. Rosario; Timimi, Bakir A.; Zimmermann, Herbert; Greco, Cristina; Ferrarini, Alberta; Storey, John M. D.; Lopez, David Orencio; Lavrentovich, Oleg D.; Luckhurst, Geoffrey R.; Imrie, Corrie T.

In: Soft matter, Vol. 12, No. 32, 2016, p. 6827-6840.

Research output: Contribution to journalArticle

Paterson, DA, Gao, M, Kim, Y-K, Jamali, A, Finley, K, Robles-Hernandez, B, Diez-Berat, S, Salud, J, de la Fuente, MR, Timimi, BA, Zimmermann, H, Greco, C, Ferrarini, A, Storey, JMD, Lopez, DO, Lavrentovich, OD, Luckhurst, GR & Imrie, CT 2016, 'Understanding the twist-bend nematic phase: the characterisation of 1-(4-cyanobiphenyl-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OCB) and comparison with CB7CB', Soft matter, vol. 12, no. 32, pp. 6827-6840. https://doi.org/10.1039/C6SM00537C
Paterson, Daniel A ; Gao, Min ; Kim, Young-Ki ; Jamali, Afsoon ; Finley, Kirsten ; Robles-Hernandez, Beatriz ; Diez-Berat, Sergio ; Salud, Josep ; de la Fuente, M. Rosario ; Timimi, Bakir A. ; Zimmermann, Herbert ; Greco, Cristina ; Ferrarini, Alberta ; Storey, John M. D. ; Lopez, David Orencio ; Lavrentovich, Oleg D. ; Luckhurst, Geoffrey R. ; Imrie, Corrie T. / Understanding the twist-bend nematic phase: the characterisation of 1-(4-cyanobiphenyl-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OCB) and comparison with CB7CB. In: Soft matter. 2016 ; Vol. 12, No. 32. pp. 6827-6840.
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abstract = "The synthesis and characterisation of the nonsymmetric liquid crystal dimer, 1-(4-cyanobiphenyl-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OCB) is reported. An enantiotropic nematic (N)-twist-bend nematic (NTB) phase transition is observed at 109˚C and a nematic-isotropic phase transition at 153˚C. The NTB phase assignment has been confirmed using polarised light microscopy, freeze fracture transmission electron microscopy (FFTEM), 2H-NMR spectroscopy, and X-ray diffraction. The effective molecular length in both the NTB and N phases indicates a locally intercalated arrangement of the molecules, and the helicoidal pitch length in the NTB phase is estimated to be 8.9 nm. The surface anchoring properties of CB6OCB on a number of aligning layers is reported. A Landau model is applied to describe high-resolution heat capacity measurements in the vicinity of the NTB-N phase transition. Both the theory and heat capacity measurements agree with a very weak first-order phase transition. A complementary extended molecular field theory was found to be in suggestive accord with the 2H-NMR studies of CB6OCB-d2, and those already known for CB7CB-d4. These include the reduced transition temperature, TNTBN/TNI, the order parameter of the mesogenic arms in the N phase close to the NTB-N transition, and the order parameter with respect to the helix axis which is related to the conical angle for the NTB phase.",
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T1 - Understanding the twist-bend nematic phase: the characterisation of 1-(4-cyanobiphenyl-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OCB) and comparison with CB7CB

AU - Paterson, Daniel A

AU - Gao, Min

AU - Kim, Young-Ki

AU - Jamali, Afsoon

AU - Finley, Kirsten

AU - Robles-Hernandez, Beatriz

AU - Diez-Berat, Sergio

AU - Salud, Josep

AU - de la Fuente, M. Rosario

AU - Timimi, Bakir A.

AU - Zimmermann, Herbert

AU - Greco, Cristina

AU - Ferrarini, Alberta

AU - Storey, John M. D.

AU - Lopez, David Orencio

AU - Lavrentovich, Oleg D.

AU - Luckhurst, Geoffrey R.

AU - Imrie, Corrie T

N1 - Acknowledgements The FFTEM data were obtained at the (Cryo) TEM facility at the Liquid Crystal Institute, Kent State University, supported by the Ohio Research Scholars Program Research Cluster on Surfaces in Advanced Materials. ODL acknowledges the support of NSF DMR-1410378 grant. The authors are grateful for financial support from MINECO/FEDER MAT2015-66208-C3-2-P and from the Gobierno Vasco (GI/IT-449-10) OA via RSC Gold4Gold

PY - 2016

Y1 - 2016

N2 - The synthesis and characterisation of the nonsymmetric liquid crystal dimer, 1-(4-cyanobiphenyl-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OCB) is reported. An enantiotropic nematic (N)-twist-bend nematic (NTB) phase transition is observed at 109˚C and a nematic-isotropic phase transition at 153˚C. The NTB phase assignment has been confirmed using polarised light microscopy, freeze fracture transmission electron microscopy (FFTEM), 2H-NMR spectroscopy, and X-ray diffraction. The effective molecular length in both the NTB and N phases indicates a locally intercalated arrangement of the molecules, and the helicoidal pitch length in the NTB phase is estimated to be 8.9 nm. The surface anchoring properties of CB6OCB on a number of aligning layers is reported. A Landau model is applied to describe high-resolution heat capacity measurements in the vicinity of the NTB-N phase transition. Both the theory and heat capacity measurements agree with a very weak first-order phase transition. A complementary extended molecular field theory was found to be in suggestive accord with the 2H-NMR studies of CB6OCB-d2, and those already known for CB7CB-d4. These include the reduced transition temperature, TNTBN/TNI, the order parameter of the mesogenic arms in the N phase close to the NTB-N transition, and the order parameter with respect to the helix axis which is related to the conical angle for the NTB phase.

AB - The synthesis and characterisation of the nonsymmetric liquid crystal dimer, 1-(4-cyanobiphenyl-4'-yloxy)-6-(4-cyanobiphenyl-4'-yl) hexane (CB6OCB) is reported. An enantiotropic nematic (N)-twist-bend nematic (NTB) phase transition is observed at 109˚C and a nematic-isotropic phase transition at 153˚C. The NTB phase assignment has been confirmed using polarised light microscopy, freeze fracture transmission electron microscopy (FFTEM), 2H-NMR spectroscopy, and X-ray diffraction. The effective molecular length in both the NTB and N phases indicates a locally intercalated arrangement of the molecules, and the helicoidal pitch length in the NTB phase is estimated to be 8.9 nm. The surface anchoring properties of CB6OCB on a number of aligning layers is reported. A Landau model is applied to describe high-resolution heat capacity measurements in the vicinity of the NTB-N phase transition. Both the theory and heat capacity measurements agree with a very weak first-order phase transition. A complementary extended molecular field theory was found to be in suggestive accord with the 2H-NMR studies of CB6OCB-d2, and those already known for CB7CB-d4. These include the reduced transition temperature, TNTBN/TNI, the order parameter of the mesogenic arms in the N phase close to the NTB-N transition, and the order parameter with respect to the helix axis which is related to the conical angle for the NTB phase.

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