Fading phenomena of azo oil dye in anionic-nonionic surfactant solutions II. Effects of alkyl and/or oxyethylene groups in nonionic surfactant on the fading rate

Abstract

Abstract:The effects of alkyl and/or oxyethylene groups in a nonionic surfactant on the fading phenomena of 4-phenylazo-l-naphthol (4-OH), which occur in aqueous solutions of anionic-nonionic surfactant systems, are described; these systems are sodium dodecyl sulfate (SDS) -alkyl poly(oxyethylene) ethers (CmPOEn, m = 12,14,16, and 18 at n = 20; n = 10, 20, 30, and 40 at m = 16). The fading phenomenon is observed when 4-OH is added to the anionic-nonionic mixed surfactant solutions at a molar ratio of i : 1. A singlet oxygen, which is caused by the hydrophilic-hydrophilic interaction between two surfactants, is thought to attack the tautomer of 4-OH. The fading rate of 4-OH accelerates with increasing alkyl chain length or with decreasing oxyethylene chain length in the nonionic surfactant molecule. The effect on the fading behavior of 4-OH would be larger for a system which can easily form a mixed micelle than for a system in which two kinds of micelles coexist.

Fading phenomena of azo oil dye in anionic-nonionic surfactant solutions III. The effect of solubilizates on the fading behavior of azo oil dye in mixed surfactant systems

“…In previous papers [6][7][8] we have reported that the fading phenomena observed in anionic-nonionic mixed surfactant solutions are caused by the singlet The singlet oxygen lifetime, however, is too short for the color of the dye to fade in surfactant-free solutions. According to Merkel and Kearns' study [14], the difference in singlet oxygen lifetime is due to kinds of solvents, which they describe in terms of intermolecular electrical-to-vibration energy transfers.…”

“…The polar nature of this acid is fairly strong and it dissociates slightly. In previous papers [6][7][8], we have reported that the fading rate of 4-OH is small in the mixed system in which two kinds of rich micelles coexist. Therefore, it is thought that anionic-rich micelles, formed easily with an increasing amount of octanoic acid solubilized, and that the fading rate of 4-OH consequently decreased with increasing its concentration.…”

“…In previous papers [6][7][8], we have reported the fading phenomena of an azo oil dye (4-phenylazo-1-naphthol, 4-OH) in anionic-nonionic mixed surfac-N 290 tant solutions. These phenomena were observed at 0.5 molar ratio of surfactant.…”