Temperature Regulation of Crown-Mediated Ion Transport through Polymer/Liquid Crystal Composite Membranes: Remarkable Transport Ability of Fluorocarbon-Containing Crown Ethers

Seiji Shinkai, Kazufumi Torigoe, Osamu Manabe, Tisato Kajiyama

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

Ternary composite membranes composed of polymer (polycarbonate, PC), liquid crystal [N-(4-ethoxy-benzylidene)-4'-butylaniline, EBBA], and crown ethers having a hydrocarbon chain (la, lb, and lc) or a fluorocarbon chain (2b and 2c) have been prepared. The DSC study established that the hydrocarbon-containing crown ethers are dissolved homogeneously in the PC/EBBA membrane, whereas the fluorocarbon-containing crown ethers form microheterogeneous, phase-separated aggregates in the membrane. Transport of K+ion through the PC/EBBA/1 membranes occurred below and above tkn (crystal-nematic liquid crystal phase-transition temperature of EBBA, 305 K), and the transport rates were faster above tkn. This indicates that carrier-mediated K+transport is directly affected by the fluidity of the membrane phase. The PC/EBBA/2 membranes provided two unexpected transport characteristics: K+transport through these membranes is “completely” suppressed below TKNand (ii) K+was transported rapidly above TKN(21–23 times faster than with the PC/EBBA/la membrane). This unusual transport ability was rationalized, on the basis of the DSC studies and the thermodynamic studies, in terms of “phase-separation” and “desolvation” characteristic of the fluorocarbon-containing crown ethers. The Arrhenius thermodynamic parameters showed a good enthalpy-entropy compensation relationship (r = 0.999) expressed by log Ea(kJ mol-1) = 5.69 log A + 52.7, but the transport rates were correlated with the increase in the entropy term. This supports the importance of the membrane fludity in efficient ion transport. The PC/EBBA/2b membrane was applied to ion-selective membrane transport and to temperature regulation of ion transport rates. The membrane transport data showed a pronounced K+selectively probably because of the formation of a 1:2 metal-crown sandwich complex between K+and aggregated 2b. Also, we could observe a reversible, all-or-northing change in the K+transport rate that was induced by the on-off-type temperature change. Thus, the PC/EBBA/2 membranes act as an ideal thermocontrolled system for K+transport: no transport below TKNand very efficient transport above TKN.

Original languageEnglish
Pages (from-to)4458-4464
Number of pages7
JournalJournal of the American Chemical Society
Volume109
Issue number15
DOIs
Publication statusPublished - Jul 1 1987
Externally publishedYes

Fingerprint

polycarbonate
Crown Ethers
Fluorocarbons
Crown ethers
Composite membranes
Liquid crystal polymers
Ion Transport
Crowns
Ions
Membranes
Polycarbonates
Temperature
Hydrocarbons
Entropy
Thermodynamics
liquid crystal polymer
Ion selective membranes
Liquid Crystals
Fluidity
Nematic liquid crystals

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

Cite this

Temperature Regulation of Crown-Mediated Ion Transport through Polymer/Liquid Crystal Composite Membranes : Remarkable Transport Ability of Fluorocarbon-Containing Crown Ethers. / Shinkai, Seiji; Torigoe, Kazufumi; Manabe, Osamu; Kajiyama, Tisato.

In: Journal of the American Chemical Society, Vol. 109, No. 15, 01.07.1987, p. 4458-4464.

Research output: Contribution to journalArticle

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