Aggregation of morpholinium surfactants with amino alcohols as additives: a close look

Mono-, di-, triethanolamine in a combination with methylmorpholinium and hydroxyethylmorpholinium surfactants were investigated for their aggregation and solubilizing properties. A cooperative behavior of the solubilization by mixed surfactant – ethanolamine systems is described. Ethanolamines strongly affect pH and lead to Orange OT phenolic group deprotonation and subsequent increase in aqueous/micellar solubility. The morpholinium surfactant micelles reduce pKa of Orange OT phenolic group, enabling its deprotonation at the earlier stages of media alkalinization. Obtained surfactant – ethanolamine mixtures can solubilize very large amounts of hydrophobic dye, which can then be triggered to precipitate via acidification.