Thermodynamics of micellization of cationic dimeric (gemini) surfactants

In the present work, the thermodynamics of the micellization process of three alkanediyl-alpha,omega-bis(dodecyldimethylammonium bromide) dimeric (gemini) surfactants with the alkanediyl spacer groups C2H4, C6H12 and C10H20 has been investigated by microcalorimetry and conductometry. This aim of the study was to understand better the behavior of cationic gemini surfactants in aqueous solution with particular emphasis on the effect of the length of the spacer group on the structure of the aggregates. This parameter appears capable of influencing the surfactant properties in water. The variations of the differential and cumulative molar enthalpies of dilution of the three gemini surfactants in water solution have been evaluated and the conductivity variations in aqueous solution were measured. The effect of the length of the spacer on the surfactant micellization process is evidenced and different micellar structures are proposed.