Order and dynamics of rod-like and banana-shaped liquid crystals by 2H NMR

Deuterium NMR spectroscopy is a very powerful technique for studying partially or totally ordered systems, such as liquid crystals (LCs) and polymers. LCs represent a branch of the most general class of soft materials, with peculiar physical and chemical properties which attracted scientific attention for their potentiality for technological applications. From a chemical point of view, there are three aspects in which 2H NMR could provide significant insights: (i) the conformational and structural properties; (ii) the molecular dynamics and mobility; and (iii) the orientational order and aggregation/distribution of molecules in the different liquid-crystalline phases. In this work, some of the recent developments in this field are discussed, focusing on two main topics: (1) the molecular dynamics of the smectic liquid-crystalline phases formed by rod-like molecules and (2) the unusual orientational and dynamic properties of the new liquid-crystalline mesophases formed by banana-shaped molecules (BLCs).

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Tracer diffusion in perfectly aligned liquid crystalline phases Kinetic theory and molecular dynamics simulations

Molecular Physics ◽

10.1080/00268979709482789 ◽

1997 ◽

Vol 91 (6) ◽

pp. 993-1003 ◽

Cited By ~ 1

Author(s):

ANJALI KHARE ◽

DAVID KOFKE ◽

GLENN EVANS

Keyword(s):

Molecular Dynamics ◽

Kinetic Theory ◽

Molecular Dynamics Simulations ◽

Liquid Crystalline ◽

Tracer Diffusion ◽

Crystalline Phases ◽

Liquid Crystalline Phases ◽

Dynamics Simulations

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Y-shaped tricatenar azobenzenes – functional liquid crystals with synclinic–anticlinic transitions and spontaneous helix formation

Journal of Materials Chemistry C ◽

10.1039/d0tc03321a ◽

2020 ◽

Vol 8 (37) ◽

pp. 12902-12916 ◽

Cited By ~ 1

Author(s):

Mohamed Alaasar ◽

Silvio Poppe ◽

Yu Cao ◽

Changlong Chen ◽

Feng Liu ◽

...

Keyword(s):

Liquid Crystals ◽

Mirror Symmetry ◽

Liquid Crystalline ◽

Crystalline Phases ◽

Helix Formation ◽

Liquid Crystalline Phases ◽

Bicontinuous Cubic

The photoisomerizable functional azobenzene unit is organized in synclinic hexatic, anticlinic smectic and bicontinuous cubic liquid crystalline phases as well as in achiral or mirror symmetry broken isotropic network liquids.

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Self-assembly and molecular dynamics studies of an excimer emissive hexacatenar derivative in helical columnar crystalline and liquid crystalline phases

Dyes and Pigments ◽

10.1016/j.dyepig.2020.108616 ◽

2020 ◽

Vol 182 ◽

pp. 108616

Author(s):

Manh Linh Nguyen ◽

Ho-Joong Kim ◽

Byoung-Ki Cho

Keyword(s):

Molecular Dynamics ◽

Self Assembly ◽

Liquid Crystalline ◽

Crystalline Phases ◽

Liquid Crystalline Phases

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Contribution of Proton NMR Relaxation to the Investigation of Molecular Dynamics and Molecular Organisation in Liquid Crystalline Phases

Molecular Crystals and Liquid Crystals Science and Technology Section A Molecular Crystals and Liquid Crystals ◽

10.1080/10587250108025776 ◽

2001 ◽

Vol 362 (1) ◽

pp. 289-304 ◽

Cited By ~ 8

Author(s):

A. C. Ribeiro ◽

P. J. Sebastião ◽

C. Cruz

Keyword(s):

Molecular Dynamics ◽

Liquid Crystalline ◽

Proton Nmr ◽

Nmr Relaxation ◽

Crystalline Phases ◽

Liquid Crystalline Phases ◽

Molecular Organisation

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

International Journal of Molecular Sciences ◽

10.3390/ijms21145024 ◽

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.

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