Charge Ordering Induces a Smectic Phase in Oblate Ionic Liquid Crystals

Ganzenmüller, Georg; Patey, G. N.

doi:10.1103/physrevlett.105.137801

Cited by 22 publications

(12 citation statements)

References 26 publications

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“…We conclude that the ionic smectic A phase is formed (counter-intuitively) with significantly lower value of the molecular order parameter S when comparing to non-ionic smectic mesogens [20][21][22]. Theoretical and computational studies suggest that, in contrast to neutral mesogens, the orientational ordering is less important for the stabilization of the smectic layers in ILC where dominant stabilizing effect is due to a "charge-ordered" nanoscale segregation induced by ionic interactions [1,19,23,24]. In order to analyse the dipolar couplings and local bond order parameters in the imidazolium core (Figure 4a), the molecular axis alignment to imidazolium ring plane has to be correctly accounted for.…”

Section: Order Parametersmentioning

confidence: 79%

Molecular and Segmental Orientational Order in a Smectic Mesophase of a Thermotropic Ionic Liquid Crystal

2018

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We investigate conformational dynamics in the smectic A phase formed by the mesogenic ionic liquid 1-tetradecyl-3-methylimidazolium nitrate. Solid-state high-resolution 13C nuclear magnetic resonance (NMR) spectra are recorded in the sample with the mesophase director aligned in the magnetic field of the NMR spectrometer. The applied NMR method, proton encoded local field spectroscopy, delivers heteronuclear dipolar couplings of each 13C spin to its 1H neighbours. From the analysis of the dipolar couplings, orientational order parameters of the C–H bonds along the hydrocarbon chain were determined. The estimated value of the molecular order parameter S is significantly lower compared to that in smectic phases of conventional non-ionic liquid crystals.

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Section: Order Parametersmentioning

confidence: 79%

Molecular and Segmental Orientational Order in a Smectic Mesophase of a Thermotropic Ionic Liquid Crystal

2018

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“…Hence, water promotes diffusion within the layers to a larger extent compared to that in the perpendicular direction. In smectic ILCs, the dominant layer-stabilising effect is due to a 'charge-ordered' nanoscale segregation induced by ionic interactions, while the orientational ordering is less important [1,41,48,49]. Water molecules contribute further to the structure stabilisation by the formation of a hydrogen bonding network in the ionic sub-layers [1].…”

Section: Diffusion In a Smectic A Phase Of A Hydrated C 12 Mimclmentioning

confidence: 99%

Nuclear magnetic resonance studies of translational diffusion in thermotropic ionic liquid crystals

Dvinskikh

2019

Liquid Crystals

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The NMR methodologies employed for investigating translational diffusion in anisotropic fluids and the results of their applications to ionic liquid crystals are reviewed. Experiments on ionic liquid crystals are preferably performed using oriented samples and require magnetic field gradients in orthogonal directions. Diffusion experiments in anisotropic systems with broad NMR lines are performed using line narrowing techniques and by application of strong static or pulsed field gradients for efficient gradient encoding/decoding of the spatial locations of molecules. Self-diffusion studies on various thermotropic ion-conductive materials exhibiting smectic, cubic, and columnar phases have been reported. Diffusion rates and anisotropy characterise the translational dynamics of ions in nanostructures and reflect the molecular ordering and ion pairing/dissociation processes. Distinct diffusion behaviours were observed for cations and anions. The knowledge of molecular mobility in ionic liquid crystals is important for the understanding their dynamic properties and is, therefore, valuable for the development of anisotropic soft materials for ion transport.

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“…Additionally, the phase diagram in hydroscopic ILCs is affected by water-anion hydrogen bonding [1,6,9]. Theoretical and experimental studies of orientational order in ILCs [1,[10][11][12][13][14] revealed that, due to the contribution of the electrostatic interactions to the stabilization of layered structures, smectic phases in ILCs exhibit significantly lower value of the molecular orientational order parameter S as compared to that in its non-ionic counterparts. However, systematic studies of the orientational order parameter depending on ILCs structure and ionic composition are still lacking.…”

Section: Introductionmentioning

confidence: 99%

NMR Spectroscopic Study of Orientational Order in Imidazolium-Based Ionic Liquid Crystals

et al. 2019

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We report on molecular and local orientational order of a series of imidazolium-based ionic liquid crystals exhibiting layered smectic A mesophase. Materials constituting of 1-dodecyl-3-methylimidazolium cation, and different counter-ions, were investigated. We apply two-dimensional 13C-1H dipolar NMR spectroscopy to quantify orientational order of C-H bonds of the organic cation. The experimental data supported the structural model of the interdigitated chains aligned with the smectic layer normal. Molecular order parameter S was found to increase in the anion sequence BF4− < I− < Br− < Cl−. This trend correlates well with ionic radius, negative charge delocalization, and hydrogen-bonding properties of the anions.

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Charge Ordering Induces a Smectic Phase in Oblate Ionic Liquid Crystals

Cited by 22 publications

References 26 publications

Molecular and Segmental Orientational Order in a Smectic Mesophase of a Thermotropic Ionic Liquid Crystal

Molecular and Segmental Orientational Order in a Smectic Mesophase of a Thermotropic Ionic Liquid Crystal

Nuclear magnetic resonance studies of translational diffusion in thermotropic ionic liquid crystals

NMR Spectroscopic Study of Orientational Order in Imidazolium-Based Ionic Liquid Crystals

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