Understanding ionic mesophase stabilization by hydration: a solid-state NMR study

Majhi, Debashis; Dai, Jing; Komolkin, Andrei V.; Dvinskikh, Sergey V.

doi:10.1039/d0cp01511c

Cited by 12 publications

(26 citation statements)

References 70 publications

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“…The representative 13 C NMR spectrum of the C 12 C 12 im ions in the smectic A phase is shown in Figure 2 . The assignment of the resolved carbon signals was performed by comparison to spectra of asymmetric analogues [ 19 , 20 , 21 , 22 ] and was confirmed by the multidimensional correlation spectra described below. The observed chemical shift (CS) was given by the component δ ⊥ of the residual CS tensor [ 18 , 20 ].…”

Section: Resultsmentioning

confidence: 99%

“…The order parameter obtained in symmetrically-substituted ILCs is higher compared to the single chain analogues [ 19 , 20 , 21 ]. In ionic liquid crystals, electrostatic and hydrogen bonding in ionic sublayer and van der Waals forces of the apolar domains are the major interactions contributing to mesophase stabilization.…”

Section: Resultsmentioning

confidence: 99%

“…NMR spectroscopy is a powerful experimental tool to non-invasively obtain high-resolution information on molecular structure and the mobility of materials in liquid-crystalline phases [ 18 ]. Anisotropic spin interactions, such as dipolar or quadrupolar couplings, have provided information on molecular ordering, director alignment, local dynamics, and conformation in ILCs [ 19 , 20 , 21 , 22 , 23 ]. Such a wide range of information in a single method is not possible to obtain with any other spectroscopic technique.…”

Section: Introductionmentioning

confidence: 99%

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

Majhi

Komolkin

Dvinskikh

2020

IJMS

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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.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Majhi

Komolkin

Dvinskikh

2020

IJMS

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“…The degree of orientational ordering has been found to correlate well with physicochemical properties of anions and increased with a phase stability range 25 . On the other hand, an expanded H-bond network in hydrated materials led to higher phase stability with a simultaneous decrease of the order parameter 26 . We have demonstrated that the enhanced contribution of van der Waals interactions in double-chain ILCs led to a greatly increased order parameter 27 .…”

Section: Ionic Liquids Crystals Belong To a Special Class Of Ionic LImentioning

confidence: 99%

“…We have previously shown that the S value in ILCs greatly varied depending on structural details [24][25][26][27] . In single-chain monocationic ILCs, a fragile balance of intermolecular forces led to low S values [24][25][26][28][29][30] . The degree of orientational ordering has been found to correlate well with physicochemical properties of anions and increased with a phase stability range 25 .…”

Section: Ionic Liquids Crystals Belong To a Special Class Of Ionic LImentioning

confidence: 99%

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

Majhi

Dvinskikh

2021

Sci Rep

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Ionic 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.

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Current Topics in Ionic Liquid Crystals

et al. 2021

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Ionic liquid crystals (ILCs), that is, ionic liquids exhibiting mesomorphism, liquid crystalline phases, and anisotropic properties, have received intense attention in the past years. Among others, this is due to their special properties arising from the combination of properties stemming from ionic liquids and from liquid crystalline arrangements. Besides interesting fundamental aspects, ILCs have been claimed to have tremendous application potential that again arises from the combination of properties and architectures that are not accessible otherwise, or at least not accessible easily by other strategies. The current review highlights recent developments in ILC research, starting with some key fundamental aspects. Further subjects covered include the synthesis and variations of modern ILCs, including the specific tuning of their mesomorphic behavior. The review concludes with reflections on some applications that may be within reach for ILCs and finally highlights a few key challenges that must be overcome prior and during true commercialization of ILCs.

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Understanding ionic mesophase stabilization by hydration: a solid-state NMR study

Abstract: Water-enhanced hydrogen-bonding network in ionic sublayer supports the formation of a thermodynamically stable smectic phase of less-ordered molecules.

Cited by 12 publications

References 70 publications

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

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

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

Current Topics in Ionic Liquid Crystals

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