Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

The aggregation behavior of ester-containing cationic gemini surfactants, dodecyl esterquat and dodecyl betainate geminis was investigated using tensiometry, conductometry, viscometry, dynamic light scattering (DLS), transmission electron microscopy (TEM) and optical microscopy techniques in the absence and presence of NaBr electrolyte. The effect of chemical structure (i.e. the presence of ester bond in alkyl chain and the spacer length)on physicochemical properties and morphology of the surfactants was studied. The results showed that the ester-containing gemini surfactants formed spherical aggregates at dilute concentration (1.1%wt). At higher concentration (3.7 %wt) the morphology is different depending on the position of ester bond in alkyl chain and the spacer length. Dodecyl betainate gemini with short spacer (s = 2) formed gel as a result of the formation of worm-like micelles in the aqueous solution. Dodecyl betainate gemini (s = 3) formed large vesicles enclosing smaller ones and dodecyl esterquat gemini (s = 3) formed both short cylindrical and spherical micelles. The salt addition induced the growth of micelles and in the case of dodecyl betainate (s = 2) gemini changed the morphology from worm-like micelles to lamellar phase.