title: Lyotropic and interfacial behaviour of an anionic gemini surfactant.
abstract: The sodium salt of N,N'-hexane-bis (1-dodecen-1-ylsuccinamic acid) is an anionic dimeric (gemini) surfactant. A flooding penetration scan of this surfactant in water demonstrates a sequence of lyotropic phases at room temperature (20 degrees C). Preparation of surfactant-water mixtures has resulted in a phase diagram which shows that the same sequence of phases exists up to 100 degrees C. These phases are tentatively assigned to the sequence: micellar to normal hexagonal (H1) to cubic (V1) to lamellar (Lalpha). The interfacial tension at the n-heptane/water interface has been determined in the presence of this surfactant. The surfactant head group area at the interface is large (2.8+/-0.3 nm2 at 298 K) and the interfacial tension above the critical micelle concentration is low (7 mN m(-1)), but considerably higher than the ultra-low values that have been reported for cationic dimeric surfactants at various hydrocarbon-water interfaces.
authors.affiliation: School of Applied Sciences, Ellison Building, Northumbria University, Newcastle upon Tyne, NE1 8ST, United Kingdom. les.dix@unn.ac.uk
authors.forename: Leslie R
authors.initials: LR
authors.lastname: Dix
authors.forename: Remi
authors.initials: R
authors.lastname: Gilblas