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

Crystals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 18 ◽  
Author(s):  
Jing Dai ◽  
Boris Kharkov ◽  
Sergey Dvinskikh
Keyword(s):  
Ionic Liquid ◽  
Conformational Dynamics ◽  
Orientational Order ◽  
Hydrocarbon Chain ◽  
Dipolar Couplings ◽  
Smectic Phases ◽  
13C Nuclear Magnetic Resonance ◽  
Smectic Mesophase ◽  
Ionic Liquid Crystals ◽  
The Magnetic Field

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.

scholarly journals Ion conformation and orientational order in a dicationic ionic liquid crystal studied by solid-state nuclear magnetic resonance spectroscopy

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Debashis Majhi ◽  
Sergey V. Dvinskikh
Keyword(s):  
Ionic Liquid ◽  
Ionic Liquids ◽  
Liquid Crystals ◽  
Bond Order ◽  
Van Der Waals ◽  
Orientational Order ◽  
Smectic Phase ◽  
Side Chains ◽  
Dicationic Ionic Liquid ◽  
Ionic Liquid Crystals

AbstractIonic liquids crystals belong to a special class of ionic liquids that exhibit thermotropic liquid-crystalline behavior. Recently, dicationic ionic liquid crystals have been reported with a cation containing two single-charged ions covalently linked by a spacer. In ionic liquid crystals, electrostatic and hydrogen bonding interactions in ionic sublayer and van der Waals interaction in hydrophobic domains are the main forces contributing to the mesophase stabilization and determining the molecular orientational order and conformation. How these properties in dicationic materials are compared to those in conventional monocationic analogs? We address this question using a combination of advanced NMR methods and DFT analysis. Dicationic salt 3,3′-(1,6-hexanediyl)bis(1-dodecylimidazolium)dibromide was studied. Local bond order parameters of flexible alkyl side chains, linker chain, and alignment of rigid polar groups were analyzed. The dynamic spacer effectively “decouples” the motion of two ionic moieties. Hence, local order and alignment in dicationic mesophase were similar to those in analogous single-chain monocationic salts. Bond order parameters in the side chains in the dicationic smectic phase were found consistently lower compared to double-chain monocationic analogs, suggesting decreasing contribution of van der Waals forces. Overall dication reorientation in the smectic phase was characterized by low values of orientational order parameter S. With increased interaction energy in the polar domain the layered structure is stabilized despite less ordered dications. The results emphasized the trends in the orientational order in ionic liquid crystals and contributed to a better understanding of interparticle interactions driving smectic assembly in this and analogous ionic mesogens.

scholarly journals NMR Spectroscopic Studies of Cation Dynamics in Symmetrically-Substituted Imidazolium-Based Ionic Liquid Crystals

2020 ◽  
Vol 21 (14) ◽  
pp. 5024
Author(s):  
Debashis Majhi ◽  
Andrei V. Komolkin ◽  
Sergey V. Dvinskikh
Keyword(s):  
Ionic Liquid ◽  
Liquid Crystals ◽  
Liquid Crystalline ◽  
Orientational Order ◽  
Soft Materials ◽  
Spectroscopic Studies ◽  
Single Chain ◽  
Self Assembling ◽  
Ionic Liquid Crystals ◽  
Cation Size

Ionic liquid crystals (ILCs) present a new class of non-molecular soft materials with a unique combination of high ionic conductivity and anisotropy of physicochemical properties. Symmetrically-substituted long-chain imidazolium-based mesogenic ionic liquids exhibiting a smectic liquid crystalline phase were investigated by solid state NMR spectroscopy and computational methods. The aim of the study was to reveal the correlation between cation size and structure, local dynamics, and orientational order in the layered mesophase. The obtained experimental data are consistent with the model of a rod-shaped cation with the two chains aligned in opposite directions outward from the imidazolium core. The alignment of the core plane to the phase director and the restricted conformations of the chain segments were determined and compared to those in single-chain counterparts. The orientational order parameter S~0.5–0.6 of double-chain ionic liquid crystals is higher than that of corresponding single-chain analogues. This is compatible with the enhanced contribution of van der Waals forces to the stabilization of smectic layers. Increased orientational order for the material with Br− counterions, which exhibit a smaller ionic radius and higher ability to form hydrogen bonds as compared to that of BF4−, also indicated a non-negligible influence of electrostatic and hydrogen bonding interactions. The enhanced rod-shape character and higher orientational order of symmetrically-substituted ILCs can offer additional opportunities in the design of self-assembling non-molecular materials.

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

Crystals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 495 ◽  
Author(s):  
Jing Dai ◽  
Debashis Majhi ◽  
Boris B. Kharkov ◽  
Sergey V. Dvinskikh
Keyword(s):  
Ionic Liquid ◽  
Liquid Crystals ◽  
Structural Model ◽  
Orientational Order ◽  
Smectic Layer ◽  
Charge Delocalization ◽  
Smectic A ◽  
Counter Ions ◽  
Bonding Properties ◽  
Ionic Liquid Crystals

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.

Adiabatic scanning calorimetry study of ionic liquid crystals with highly ordered crystal smectic phases

2013 ◽  
Vol 40 (3) ◽  
pp. 329-338 ◽  
Author(s):  
Chandra Shekhar Pati Tripathi ◽  
Jan Leys ◽  
Patricia Losada-Pérez ◽  
Kathleen Lava ◽  
Koen Binnemans ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Liquid Crystals ◽  
Scanning Calorimetry ◽  
Adiabatic Scanning Calorimetry ◽  
Smectic Phases ◽  
Ionic Liquid Crystals

scholarly journals Smectic phases in ionic liquid crystals

2017 ◽  
Vol 29 (46) ◽  
pp. 464002 ◽  
Author(s):  
Hendrik Bartsch ◽  
Markus Bier ◽  
S Dietrich
Keyword(s):  
Ionic Liquid ◽  
Liquid Crystals ◽  
Smectic Phases ◽  
Ionic Liquid Crystals

Molecular dynamics and electrical conductivity of Guanidinium based ionic liquid crystals: Influence of cation headgroup configuration

2021 ◽  
Vol 330 ◽  
pp. 115666
Author(s):  
Mohamed A. Kolmangadi ◽  
Arda Yildirim ◽  
Kathrin Sentker ◽  
Martin Butschies ◽  
Andrea Bühlmeyer ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Electrical Conductivity ◽  
Ionic Liquid ◽  
Liquid Crystals ◽  
Ionic Liquid Crystals
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