TY - JOUR

T1 - Understanding ionic mesophase stabilization by hydration

T2 - a solid-state NMR study

AU - Majhi, Debashis

AU - Dai, Jing

AU - Komolkin, Andrei V.

AU - Dvinskikh, Sergey V.

N1 - Publisher Copyright: © 2020 the Owner Societies.

PY - 2020/6/28

Y1 - 2020/6/28

N2 - The correlation between the water contribution to hydrogen bonding within ionic sublayer, mesophase order parameter, and ion translational self-diffusion in the layered ionic liquid crystalline phase is investigated. Changes in hydrogen bonding, conformational and translational dynamics, and orientational order upon hydration were followed by solid-state NMR combined with density functional theory (DFT) analysis. We observed that the smectic mesophase of monohydrated imidazolium-based ionic liquids, which was stabilized in a wider temperature range compared to that of anhydrous materials, counterintuitively exhibited a lower orientational order of organic cations. Thus the role of anisotropic alignment of cations and contribution of dispersion forces in the mesophase stability decreased upon hydration. The local dynamics of cations is controlled by the alignment of the bulky methyl-imidazolium ring, experiencing strong electrostatic and H-bond interactions in the ionic sublayer. Anisotropy of translational diffusion increased in the hydrated samples, thus supporting the layer-stabilizing effect of water. The effect of decreasing molecular order is outweighed by the contribution of water hydrogen bonding to the overall interaction energy within the ionic sublayer.

AB - The correlation between the water contribution to hydrogen bonding within ionic sublayer, mesophase order parameter, and ion translational self-diffusion in the layered ionic liquid crystalline phase is investigated. Changes in hydrogen bonding, conformational and translational dynamics, and orientational order upon hydration were followed by solid-state NMR combined with density functional theory (DFT) analysis. We observed that the smectic mesophase of monohydrated imidazolium-based ionic liquids, which was stabilized in a wider temperature range compared to that of anhydrous materials, counterintuitively exhibited a lower orientational order of organic cations. Thus the role of anisotropic alignment of cations and contribution of dispersion forces in the mesophase stability decreased upon hydration. The local dynamics of cations is controlled by the alignment of the bulky methyl-imidazolium ring, experiencing strong electrostatic and H-bond interactions in the ionic sublayer. Anisotropy of translational diffusion increased in the hydrated samples, thus supporting the layer-stabilizing effect of water. The effect of decreasing molecular order is outweighed by the contribution of water hydrogen bonding to the overall interaction energy within the ionic sublayer.

KW - LOCAL-FIELD SPECTROSCOPY

KW - SMECTIC-A-PHASE

KW - LIQUID-CRYSTALS

KW - 1-DODECYL-3-METHYLIMIDAZOLIUM BROMIDE

KW - MESOMORPHIC BEHAVIOR

KW - NATURAL-ABUNDANCE

KW - HYDROGEN-BONDS

KW - C-13 NMR

KW - DYNAMICS

KW - SALTS

UR - http://www.scopus.com/inward/record.url?scp=85087095458&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/8d6c1435-079c-31f4-adf6-16370682cccd/

U2 - 10.1039/d0cp01511c

DO - 10.1039/d0cp01511c

M3 - Article

C2 - 32510078

AN - SCOPUS:85087095458

VL - 22

SP - 13408

EP - 13417

JO - Physical Chemistry Chemical Physics

JF - Physical Chemistry Chemical Physics

SN - 1463-9076

IS - 24

ER -