Liquid crystal diffusion in thin films investigated by PFG magnetic resonance and magnetic resonance imaging

Zhang, Jing; MacGregor, R.; Balcom, Bruce J.

doi:10.1016/j.cplett.2008.06.090

Cited by 8 publications

(3 citation statements)

References 23 publications

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Section: Resultssupporting

confidence: 92%

“…The liquid crystalline phases exhibited an activation energy of 27.02 kJ/mol while the isotropic phase exhibited an activation energy of 39.33 kJ/mol. These values were consistent with the literature values calculated from self-diffusion data (33 kJ/mol for the nematic and isotropic phase of 4-cyano-4′-pentylbiphenyl (5CB); 44 31 kJ/mol for the isotropic phase and 23 kJ/mol for the nematic phase of N-(pmethoxy-benzylidene)-p-n-butylaniline (MBBA) 45 ) It is also consistent with the previous research indicating that activation energies increase as the ordering of liquid crystal decreases through the smectic or cholesteric to the isotropic phase as determined using gas chromatography 46 and nuclear magnetic resonance (NMR). 44,45,47 When Vilfan et al 44 studied the self-diffusion coefficients of 5CB using NMR, a discontinuous jump in the selfdiffusivity for the same activation energy was found at the isotropic to nematic phase transition for bulk 5CB due to anisotropy in the nematic phase (where only the anisotropic self-diffusion tensor along the nematic director was considered).…”

Section: Resultssupporting

confidence: 91%

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Diffusivity and Solubility of Organic Solutes in Supported Liquid Crystal Membranes

Han

Martin

2009

J. Phys. Chem. B

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The electro-optical properties of thermotropic liquid crystalline (LC) materials have been the subject of significant research effort due to their well-established applications in display technology; however, relatively little work has been done concerning the transport of dissolved solutes in LC phases, limiting their potential use in applications including chemical separation and sensing. Supported liquid crystal membranes were synthesized by impregnating porous cellulose nitrate (CN) membranes with 4-cyano-4'-octylbiphenyl (8CB) from chloroform solutions under vacuum. The resulting membranes were stable under aqueous conditions. Measurements of the 8CB-CN membrane transport properties were performed at 38 degrees C (nematic) and 44 degrees C (isotropic) for 11 aromatic solutes, including positional isomers, in aqueous solution. Solute diffusivity and solubility was calculated using a time-lag technique based on the study of the transient (unsteady state) and steady-state permeation regimes. The solubility and diffusivity of aqueous aromatic solutes in 8CB LCs depended significantly on intra- and intermolecular hydrogen bonding, and more specifically the number of hydrogen-bonding sites on a solute that are available for interactions with the aqueous and LC phases. In the nematic phase of 8CB, shape specific affinity was observed for para isomers and other rodlike solutes. A decreased activation energy for diffusion was observed at the isotropic to nematic phase transition for o-hydroxybenzoic acid, as expected based on the increased order in the nematic phase. Permeation selectivities for the separation of positional isomers by the 8CB-CN membranes indicated high selectivity only for the hydroxybenzoic acid isomers, due to the propensity of o-hydroxybenzoic acid to form intramolecular hydrogen bonds.

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 91%

Diffusivity and Solubility of Organic Solutes in Supported Liquid Crystal Membranes

Han

Martin

2009

J. Phys. Chem. B

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“…Solid-state NMR relaxometry has established its position in food science, including the determination of moisture content, solid fat content and much more [203] and shown to be complementary to traditional microscopic techniques in studying the phase morphology of blended materials used in semiconductive polymer-based devices [204].…”

Section: Advanced Hyperpolarization Techniquesmentioning

confidence: 99%

Solid State NMR Spectroscopy a Valuable Technique for Structural Insights of Advanced Thin Film Materials: A Review

Nokab

Sebakhy

2021

Nanomaterials

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Solid-state NMR has proven to be a versatile technique for studying the chemical structure, 3D structure and dynamics of all sorts of chemical compounds. In nanotechnology and particularly in thin films, the study of chemical modification, molecular packing, end chain motion, distance determination and solvent-matrix interactions is essential for controlling the final product properties and applications. Despite its atomic-level research capabilities and recent technical advancements, solid-state NMR is still lacking behind other spectroscopic techniques in the field of thin films due to the underestimation of NMR capabilities, availability, great variety of nuclei and pulse sequences, lack of sensitivity for quadrupole nuclei and time-consuming experiments. This article will comprehensively and critically review the work done by solid-state NMR on different types of thin films and the most advanced NMR strategies, which are beyond conventional, and the hardware design used to overcome the technical issues in thin-film research.

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Optimization of a parallel‐plate RF probe for high resolution thin film imaging

Aguilera

MacMillan

Goward

et al. 2018

Concepts Magnetic Resonance

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Choosing an MR probe with the correct dimensions and high sensitivity is critical for magnetic resonance imaging, especially high resolution thin film imaging. In this work, a parallel‐plate resonator has been optimized for strength and uniformity of the B1 magnetic field. The parallel‐plate resonator is designed for high resolution imaging in the direction perpendicular to the plates. The optimization process was undertaken through simulation with CST Micro Wave Studio, followed by experiment. A 400 μm capillary tube, filled with doped water, was used for testing the optimized probe in a 2.4 T magnet. It is shown that increasing the width of the copper leads connected to the plates increases the homogeneity of the B1 magnetic field by almost 90%. The best approach to increase the sensitivity and the homogeneity of the probe was to maintain the dimensions of the plates and copper leads but to add additional capacitors at the corners to distribute the current. This approach produces a 40% stronger B1 magnetic field and increases the homogeneity by almost 85%. The experimental B1 magnetic field of the parallel‐plate prototype agrees within 20% of the value found through simulation, for specified power. The experimental MRI results show that it is possible to achieve a nominal resolution of 10 μm between the plates for suitable samples using the optimized probe. The optimized parallel‐plate resonator, combined with a phase encode SE SPI method, may be used for high resolution studies of lithium‐ion transport in the electrolyte solution of lithium‐ion batteries.

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Liquid crystal diffusion in thin films investigated by PFG magnetic resonance and magnetic resonance imaging

Cited by 8 publications

References 23 publications

Diffusivity and Solubility of Organic Solutes in Supported Liquid Crystal Membranes

Diffusivity and Solubility of Organic Solutes in Supported Liquid Crystal Membranes

Solid State NMR Spectroscopy a Valuable Technique for Structural Insights of Advanced Thin Film Materials: A Review

Optimization of a parallel‐plate RF probe for high resolution thin film imaging

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