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dc.contributor.authorRobles Hernández, Beatriz
dc.contributor.authorSebastian Ugarteche, Nerea
dc.contributor.authorRosario De la Fuente, M.
dc.contributor.authorLópez Pérez, David Orencio
dc.contributor.authorDíez Berart, Sergio
dc.contributor.authorSalud Puig, Josep
dc.contributor.authorRos, M. Blanca
dc.contributor.authorDunmur, D.A.
dc.contributor.authorLuckhurst, G.R.
dc.contributor.authorTimimi, Bakir A.
dc.contributor.otherUniversitat Politècnica de Catalunya. Departament de Física
dc.identifier.citationRobles-Hernández, B., Sebastian, N., Rosario, M., Lopez, D., Diez, S., Salud, J., Ros, M., Dunmur, D., Luckhurst , G., Timimi, B. Twist, tilt, and orientational order at the nematic to twist-bend nematic phase transition of 1 '',9 ''-bis(4-cyanobiphenyl-4 '-yl) nonane: A dielectric, H-2 NMR, and calorimetric study. "Physical review E: statistical, nonlinear, and soft matter physics", 02 Desembre 2015, vol. 92, núm. 6, p. 062505-1-062505-16.
dc.description.abstractThe nature of the nematic-nematic phase transition in the liquid crystal dimer 1 '',9 ''-bis(4-cyanobiphenyl-4'-yl) nonane (CB9CB) has been investigated using techniques of calorimetry, dynamic dielectric response measurements, and H-2 NMR spectroscopy. The experimental results for CB9CB show that, like the shorter homologue CB7CB, the studied material exhibits a normal nematic phase, which on cooling undergoes a transition to the twist-bend nematic phase (N-TB), a uniaxial nematic phase, promoted by the average bent molecular shape, in which the director tilts and precesses describing a conical helix. Modulated differential scanning calorimetry has been used to analyze the nature of the N-TB-N phase transition, which is found to be weakly first order, but close to tricritical. Additionally broadband dielectric spectroscopy and H-2 magnetic resonance studies have revealed information on the structural characteristics of the recently discovered twist-bend nematic phase. Analysis of the dynamic dielectric response in both nematic phases has provided an estimate of the conical angle of the heliconical structure for the N-TB phase. Capacitance measurements of the electric-field realignment of the director in initially planar aligned cells have yielded values for the splay and bend elastic constants in the high temperature nematic phase. The bend elastic constant is small and decreases with decreasing temperature as the twist-bend phase is approached. This behavior is expected theoretically and has been observed in materials that form the twist-bend nematic phase. H-2 NMR measurements characterize the chiral helical twist identified in the twist-bend nematic phase and also allow the determination of the temperature dependence of the conical angle and the orientational order parameter with respect to the director.
dc.subjectÀrees temàtiques de la UPC::Energies::Energia elèctrica
dc.subjectÀrees temàtiques de la UPC::Física::Física de l'estat sòlid
dc.subjectÀrees temàtiques de la UPC::Física::Termodinàmica
dc.subject.lcshMagnetic resonance
dc.subject.lcshElectric fields
dc.subject.otherLiquid-crystal dimers
dc.titleTwist, tilt, and orientational order at the nematic to twist-bend nematic phase transition of 1 '',9 ''-bis(4-cyanobiphenyl-4 '-yl) nonane: A dielectric, H-2 NMR, and calorimetric study
dc.subject.lemacRessonància magnètica
dc.subject.lemacCamps elèctrics
dc.rights.accessOpen Access
dc.description.versionPostprint (author's final draft)
local.citation.authorRobles-Hernández, B.; Sebastian, N.; Rosario, M.; Lopez, D.; Diez, S.; Salud, J.; Ros, M.; Dunmur, D.; Luckhurst, G.; Timimi, B.
local.citation.publicationNamePhysical review E: statistical, nonlinear, and soft matter physics

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