No abstract

To prepare anion exchange membranes which permeate specific anions selectively in electrodialysis, anion exchange membranes with various anion exchange groups were prepared and the relative transport number of various anions compared with chloride ions was examined. Anion exchange groups introduced in the membranes were trimethylbenzylammonium, triethylbenzylammonium, tri-n-propylbenzylammonium, tri-nbutylbenzylammonium, and tri-n-pentylbenzylammonium, in order of increasing hydrophobicity. The relative transport number of various anions compared with chloride ions changed remarkably with increasing chain length of alkyl groups (increasing hydrophobicity of the groups). The relative transport number of highly hydrated anions, such as sulfate ions and fluoride ions, compared with chloride ions decreased with increasing hydrophobicity of the groups. On the other hand, less hydrated anions such as bromide ions and nitrate ions compared with chloride ions permeate selectively through the membrane with increasing hydrophobicity of the groups. For example, the relative transport number of nitrate ions compared with chloride ions increased from 1.58 (membrane with trimethylbenzylammonium groups) to 16.5 (membrane with tri-n-pentylbenzylammonium groups) in electrodialysis of a 1:1 mixed solution of sodium nitrate and sodium chloride (0.04 N as sodium ion concentration). However, the increase in hydrophilicity of the membrane by further reaction of the remaining chloromethyl groups of the membrane with trimethylamine caused the relative transport number between them to decrease.

A cation exchange membrane was modified with polyaniline by polymerizing aniline with ammonium peroxodisulfate on the membrane surfaces, producing a membrane with polyaniline layers on both surfaces or a membrane with a single polyaniline layer on the surface. The modified membranes, composite membranes, showed sodium ion permselectivity in electrodialysis compared with divalent cations at an optimum polymerization time. The electronic conductivity of dry membranes showed a maximum false(normalca.5×10−3Scm−1false) at the same polymerization time as the time to attain a maximum value of the sodium ion permselectivity. Because emeraldine‐based polyaniline is conductive and has a cationic charge, the sodium ion permselectivity is based on the difference in the electrostatic repulsion forces of the cationic charge on the membrane surface of a desalting side to divalent cations and sodium ions. In fact, the selective permeation of sodium ions appeared only when the layer faced the desalting side of the membrane, and was affected by dissociation of polyaniline. Further oxidized polyaniline, pemigraniline‐based polyaniline, did not affect the permselectivity between cations, and the diffusion coefficient of neutral molecules, urea, increased with increasing polymerization time. Sodium ion permselectivity was maintained with repeated electrodialysis. © 1999 The Electrochemical Society. All rights reserved.

A high-efficiency organic light-emitting diode (OLED) microdisplay has been developed with some new technologies including microlens array. We focused on the improvement of the out-coupling efficiency and achieved three times higher efficiency as compared with conventional OLED. By using our developed technologies, it is possible to improve the maximum luminance from 1600 to 5000 cd/m 2 while maintaining same lifetime.

Anion exchange membranes with pyridinum groups and various pyridinium derivative groups were prepared from a copolymer membrane composed of chloromethylstyrene and divinylbenzene, and pyridine and pyridine derivatives. The anion exchange membranes obtained showed excellent electrochemical properties in electrodialysis. The transport numbers of sulfate ions, bromide ions, nitrate ions, and fluoride ions relative to chloride ions were evaluated in connection with the species of a substituent and the position of the substituent in the pyridinium groups. In general, when a hydrophilic substituent (methanol groups) existed at the 2‐position of the pyridinium groups, nitrate ions and bromide ions, which are less hydrated, permeated through the membranes with difficulty, and sulfate ions permeated selectively through the membranes. On the other hand, when hydrophobic groups, for example, ethyl groups, existed at the 2‐position of the pyridinium groups, bromide ions and nitrate ionspermeated selectively through the membranes and fluoride ions had difficulty permeating through the membranes. The carbon number of the alkyl chain of 4‐alkyl pyridinium groups also affected permeation of nitrate ions and bromide ions due to the change in hydrophilicity of the membranes. Though the hydration of the anions and the species of the substituent at the 2‐position of the pyridinium groups were related to selective permeation of the anion through the membranes, permeation of sulfate ions was not as sensitive to the hydrophilicity of the membranes. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 49–58, 1998