title: Dependence of ion selectivity on ordered orientation of neutral carriers in ion-sensing membranes based on thermotropic liquid crystals.
abstract: Thermotropic liquid-crystalline compounds were applied as membrane materials (membrane solvent and neutral carrier) for neutral carrier-type ion sensors to investigate how the ordered arrangement of neutral carriers affects the property of the resulting ion sensors. Nematic, smectic, and cholesteric liquid-crystalline compounds were used as the membrane solvents and crown ether derivatives with a molecular structure similar to the liquid-crystalline solvent as the K+ neutral carriers. Polarized IR spectroscopy and X-ray diffraction experiments confirmed that the highly ordered arrangement of membrane components was retained in the liquid-crystal-based ion-sensing membranes containing a neutral carrier and a lipophilic salt. The ordered arrangement of neutral carriers in the liquid-crystalline membranes enhanced the ion selectivity significantly, probably due to the efficient cooperation of two adjacent crown ether moieties in the highly ordered and aggregated state.
authors.affiliation: Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University, Japan. kkimura@sys.wakayama-u.ac.jp
authors.forename: Keiichi
authors.initials: K
authors.lastname: Kimura
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kawai
authors.forename: Shusuke
authors.initials: S
authors.lastname: Oosaki
authors.forename: Setsuko
authors.initials: S
authors.lastname: Yajima
authors.forename: Yayoi
authors.initials: Y
authors.lastname: Yoshioka
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Sakurai
mesh_terms: D003460:Crystallization; D004988:Ethers, Cyclic / Q000737:chemistry*; D017736:Ion-Selective Electrodes; D008567:Membranes, Artificial; D011188:Potassium / Q000032:analysis; D012964:Sodium / Q000032:analysis; D013055:Spectrophotometry, Infrared / Q000379:methods; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D004988:Ethers, Cyclic; D008567:Membranes, Artificial; D012964:Sodium; D011188:Potassium