m-s-m Cationic Gemini and Zwitterionic Surfactants–Spacer-Dependent Synergistic Interactions

Critical micelle concentration (cmc) values were determined for the mixed zwitterionic/cationic gemini systems of N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (ZW3–12)/N,N′-bis(dimethyldodecyl)-α,ω-alkanediammonium dibromide (12-s-12) systems. The cmc values for the mixed systems were determined through conductivity measurements. The degree of nonideality of the interaction in the mixed micelle (βm), for each system, was determined according to Rubingh’s nonideal solution theory. In most cases, the systems exhibited negative deviations (−βm values) at high surfactant mole fractions of zwittergent (αZW3–12). Specifically, the ZW3–12/12–4–12 system displayed −βm values at αZW3–12 ≥ 0.5, while both the ZW3–12/12–5–12 and the ZW3–12/12–6–12 systems displayed −βm values over the entire mole fraction range. Except for the low mole fraction range in the 12–4–12 system, these mixed surfactant systems demonstrated almost identical behavior to the n-dodecyltrimethylammonium bromide/12–2–12 system studied by ...