Mixed micelles of anionic-nonionic and anionic-zwitterionic surfactants analyzed by pulsed field gradient NMR

The micellar composition of two binary surfactant systems, that is, sodium dodecyl sulfate (SDS)/pentaethylene glycol monodecyl ether (C10E5) and SDS/ lauryl amido propyl betaine (LAPB), has been analyzed by pulsed gradient sp in-echo NMR (FT-PGSE NMR). The experimental data have been compared to theo retical predictions based on the regular solution theory that takes into ac count the nonideal mixing of the surfactant pairs. Although good agreement between experiment and theory is observed for the SDS/C10E5 pair, some disc repancy is noted for the LAPB/SDS system, particularly at a high molar frac tion of SDS.