Cation binding at the air-water interface by macromolecules bearing pendant crown ethers moieties

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Title: Cation binding at the air-water interface by macromolecules bearing pendant crown ethers moieties
Author: Gold, Jeffrey; Teegarden, David; McGrane, Kathleen; Luca, David; Falcigno, Pasquale; Chen, Cindy; Smith, Thomas
Abstract: In solution, the ion-binding characteristics of crown ethers and macromolecules containing macrocyclic ether moieties have been studied extensively. These ionophores are finding application in membranes, thin film sensors, and ion-selective electrodes. In these devices, interfacial binding equilibria are most pertinent. This paper presents the results of a detailed analysis of the pressure vs. area behavior of Langmuir films of poly(4’-vinylbenzo-18 crown-6), P18C6, spread on pure water and aqueous solutions of alkali metal salts. Our results show that the compression isotherms can be quantitatively related to the nature of the cation in the subphase and its concentration. At the air-water interface, the polymer is in a highly extended conformation and cooperative binding between proximate crown ether groups is precluded. Accordingly, the affinity of the polymer for Li+, Na+, K+, Rb+, and Cs+ at the airsolution interface mirrors that of the monomeric analogue, benzo-18-crown-6, in solution and is inverse to that of P18C6 in solution. Equilibrium binding constants for complexation of P18C6 to K+ at the air-water interface are comparable to those for binding of P18C6 to K+ in aqueous solution.
Record URI: http://hdl.handle.net/1850/2349
Publishers URL: http://dx.doi.org/10.1021/ja00279a027
Date: 1986-09-17

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