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22 results on '"Kaifu, Katsuaki"'

16. Studies of Molecular Motions in Acylchitin Films by Means of Spin-Probe Technique

Author

Kaifu, Katsuaki, Komai, Takashi, and Tsutsumi, Akihiro

Abstract

The molecular motions in acylated chitins, including acetyl, propionyl, butyryl, caproyl, capryl, lauroyl, and benzoylchitin, were investigated by ESR measurements with 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl (TEMPO) as a spin-probe. Introduction of a longer side chain into the chitin molecule resulted in a remarkable lowering of the temperature at which the separation between the outer two extrema of the ESR spectrum decreases adruptly (TN). Below and above TN, two kinds of motional process were observed, one at a lower temperature having a smaller activation energy and the other at a higher temperature with a larger activation energy. These processes are a small scale motion such as rotational oscillation and a large scale motion such as rotation, respectively. The activation energy of the latter process decreased with increasing chain length, except for acetylchitin. Fully acetylated chitin films were anomalous with respect to the value of the activation energy.

Published
1982
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17. Studies on Chitin. V. Formylation, Propionylation, and Butyrylation of Chitin

Author

Kaifu, Katsuaki, Nishi, Norio, Komai, Takashi, Tokura, Seiichi, and Somorin, Oyin

Abstract

Variously substituted propionylchitin, and butyrylchitin were prepared using the corresponding carboxylic acid, carboxylic anhydride or their mixture in methanesulfonic acid at low temperatures. Formylchitin derivatives with different degrees of formylation were prepared from a formic acid–methanesulfonic acid mixture. Highly substituted butyrylchitin is easily soluble in common organic solvents such as dioxane, tetrahydrofuran, acetone, acetonitrile, dimethyl-formamide, acetic acid, and methanol in addition to acidic solvents such as formic acid and dichloroacetic acid. Other acylchitins are soluble only in acidic solvents. The viscometric behavior of a chitin solution in methanesulfonic acid and the infrared absorption spectra of the acylchitin derivatives were also investigated.

Published
1981
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18. Synthesis and Properties of Europium Complexes with ß-Diketone Ligands for Organic Electroluminescent Devices

Author

Uekawa, Masahiro, Miyamoto, Yasuo, Ikeda, Hitoshi, Kaifu, Katsuaki, and Nakaya, Tadao

Abstract

Europium complexes with new ß-diketone ligands with fluorene for organic electroluminescent (EL) devices have been synthesized and their properties examined. The absorption spectra of the complexes were varied by changing the conjugated system of the ß-diketone; also, the energy transfer from the host material to the europium complexes and the intramolecular energy transfer have been improved. Concerning the volatility, the thermal properties of the europium complexes were improved by using phenanthroline derivatives. We fabricated organic EL devices using the synthesized complexes, and investigated the luminance of the devices.

Published
1998
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