title: Enantioselective separations using chiral supported liquid crystalline membranes.
abstract: 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%.
authors.affiliation: School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA.
authors.forename: Sangil
authors.initials: S
authors.lastname: Han
authors.forename: Feras
authors.initials: F
authors.lastname: Rabie
authors.forename: Eva
authors.initials: E
authors.lastname: Marand
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Martin
mesh_terms: D005591:Chemical Fractionation / Q000379:methods*; D002853:Chromatography, Liquid; D005998:Glycine / Q000737:chemistry; D006860:Hydrogen Bonding; D050866:Liquid Crystals / Q000737:chemistry*; D008567:Membranes, Artificial; D010539:Permeability; D010626:Phenylethyl Alcohol / Q000737:chemistry; D016062:Porosity; D013237:Stereoisomerism; D013696:Temperature
chemical_list: D008567:Membranes, Artificial; D010626:Phenylethyl Alcohol; D005998:Glycine