Study of the environmental responsiveness of amino acid-based surfactant sodium lauroylglutamate and its foam characteristics

Abstract

In this paper, the bulk phase aggregation and interfacial adsorption properties as well as foam characteristics of a kind of amino acid-based surfactant sodium lauroylglutamate (LGS) under the variety of external conditions such as temperature and pH were investigated. The variation of the protonation degree of the head group of the surfactant as a function of pH was analyzed by integrating determination results of acid-base titration and FT-IR (ATR) spectra. At neutral pH, the LGS solution had the minimum surface tension and could form more stable foam. The mechanism about how the pH affects the foam stability of LGS was discussed thoroughly. TEM images of the LGS foam films and the bulk phase solutions showed that gel network association structure was formed not only in bulk phase in specific temperature range and suitable pH, but also in the foam films. The variation of the strength of the gel formed in foam film under different external conditions has obviously different influence on foam stability.