Molecular diffusion in liquid crystals and chiral discrimination. I. Theory

Frezzato, Diego; Moro, Giorgio J.; Zannoni, Claudio

doi:10.1063/1.1884110

Cited by 15 publications

(12 citation statements)

References 21 publications

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“…However, 1‐phenylethanol enantiomers exhibited no enantioselectivity in the nonporous membranes (selectivity 1.01). This is in disagreement with the theoretical predictions of Frezzato et al . who predicted faster diffusion for one enantiomer in a chiral matrix.…”

Section: Resultscontrasting

confidence: 98%

“…25 However, 1-phenylethanol enantiomers exhibited no enantioselectivity in the nonporous membranes (selectivity 1.01). This is in disagreement with the theoretical predictions of Frezzato et al 26,27 who predicted faster diffusion for one enantiomer in a chiral matrix. It is possible that the chiral selectivity is lost because the helical axes of the cholesteric phase are not macroscopically aligned across the whole membrane thickness.…”

Section: The Effect Of Pore Size On Phenylglycine and 1-phenylethanolcontrasting

confidence: 88%

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Enantioselective separations using chiral supported liquid crystalline membranes

et al. 2012

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Porous and nonporous supported liquid crystalline membranes were produced by impregnating porous cellulose nitrate supports with cholesteric liquid crystal (LC) materials consisting of 4-cyano-4'-pentylbiphenyl (5CB) mixed with a cholesterol-based dopant (cholesteryl oleyl carbonate [COC], cholesteryl nonanoate [CN], or cholesteryl chloride [CC]). The membranes exhibit selectivity for R-phenylglycine and R-1-phenylethanol because of increased interactions between the S enantiomers and the left-handed cholesteric phase. The selectivity of both phenylglycine and 1-phenylethanol in 5CB/CN membranes decreases with effective pore diameter while the permeabilities increase, as expected. Phenylglycine, which is insoluble in the LC phase, exhibits no transport in the nonporous (completely filled) membranes; however, 1-phenylethanol, which is soluble in the LC phase, exhibits transport but negligible enantioselectivity. The enantioselectivity for 1-phenylethanol was higher (1.20 in 5CB/COC and 5CB/CN membranes) and the permeability was lower in the cholesteric phase than in the isotropic phase. Enantioselectivity was also higher in the 5CB/COC cholesteric phase than in the nematic phase of undoped 5CB (1.03). Enantioselectivity in the cholesteric phase of 5CB doped with CC (1.1), a dopant lacking hydrogen bonding groups, was lower than in the 5CB/COC phases. Finally, enantioselectivity increases with the dopant concentration up to a plateau value at approximately 17 mol%.

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Section: Resultscontrasting

confidence: 98%

Section: The Effect Of Pore Size On Phenylglycine and 1-phenylethanolcontrasting

confidence: 88%

Enantioselective separations using chiral supported liquid crystalline membranes

et al. 2012

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“…15 Our hypothesis is that the biaxiality would introduce only a minor correction to the values of D mt ͑u hx ͒ evaluated for uniaxial alignment. 15 Our hypothesis is that the biaxiality would introduce only a minor correction to the values of D mt ͑u hx ͒ evaluated for uniaxial alignment.…”

Section: Archetype Molecules and Outlines Of Model Calculationsmentioning

confidence: 97%

“…15 Intuitively, the main pitch-dependent effects on the molecular alignment are ͑i͒ a modulation of the strength of orientational ordering with respect to the local director ͑the x DF axis͒ and ͑ii͒ the appearance of phase biaxiality about such an axis. Such a dependence is due to the twist of the phase as sensed at the molecular level.…”

Section: Macroscopic Diffusion In Cholesteric Phasesmentioning

confidence: 99%

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Molecular diffusion in liquid crystals and chiral discrimination. II. Model calculations

Frezzato

Zannoni

Moro

2006

The Journal of Chemical Physics

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We perform model calculations of the macroscopic diffusion coefficient for a solute moving in a chiral nematic (cholesteric) liquid crystal (LC) phase applying the methodology developed by Frezzato et al. [J. Chem. Phys. 122, 164904 (2005)]. Three types of solutes with different features are studied: ellipsoid [roto-translational coupling (RTC) absent], bent rod (RTC present), and two-blade propeller (with RTC and chiral shape). For each prototype molecule we estimate the effect of cholesteric helix pitch and local order on the diffusion along the helix axis. For the ellipsoidal particle we find that translational diffusion is slowed down by rotation around the short axis. For the chiral solute we show that the enantiomer with shape chirality opposite to that of the LC phase is slowed down more than the other. This provides a proof of principle of the possibility of separating the two enantiomers via transport in a suitable chiral medium.

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Adsorption Phenomena and Anomalous Behavior

Evangelista

Lenzi²

2023

An Introduction to Anomalous Diffusion and Relaxation

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Molecular diffusion in liquid crystals and chiral discrimination. I. Theory

Cited by 15 publications

References 21 publications

Enantioselective separations using chiral supported liquid crystalline membranes

Enantioselective separations using chiral supported liquid crystalline membranes

Molecular diffusion in liquid crystals and chiral discrimination. II. Model calculations

Adsorption Phenomena and Anomalous Behavior

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