Comparison of Surface-Active Properties of (Alkyloxycarbonylmethyl)trimethylammonium Chlorides and Alkyltrimethylammonium Chlorides

摘要

Surface-active properties of cleavable surfactants with a betaine ester group—(n-alkyloxycarbonylmethyl)trimethylammonium chlorides, used as separation reagents—were investigated. Critical micelle concentrations, dispersing powers, and foaming powers were comparable to those of alkyltrimethylammonium chlorides with the same total number of carbon atoms. On the other hand, the solubilities of the four hydrophobic dyes N,N-dimethyl-3-nitroaniline, naphthalene, pyrene, and oil orange SS in the former surfactant solutions were equal to or slightly smaller than those in the solutions of the latter surfactants with the same alkyl chain length. The alkali hydrolysis yields of the formers approached 100% in aqueous buffer solution at pH 10 and 25 °C within 10 min, and the yield at pH 9 was dependent on the alkyl chain length. This type of surfactant was also found to be as an efficient separation reagent which disperses carbon black and solubilizes the above dyes into aqueous neutral solution and then separates them instantaneously and almost perfectly as precipitates when a small excess of NaOH is added.