Nature of the oil/water interface and equilibrium surfactant aggregates in systems exhibiting low tensions

Abstract

. Can. J. Chem. 66, 000 (1988). Oillwater interfacial tensions are reported for systems containing pure alkane, aqueous sodium chloride, and a pure anionic surfactant, either Aerosol OT or p-dihexylbenzene sodium sulphonate (DHBS). Evidence is produced to support the claim that monolayer adsorption at the oillwater interface can produce ultralow tensions (-1 pN m-I), and that the presence at the interface of a third, surfactant-rich phase is not necessary. The aggregation of DHBS and its distribution between oil and aqueous phases of various salinities have been investigated. It has been confirmed that the behaviour of DHBS in these respects is similar to that of Aerosol OT, as might be expected from its molecular structure. The sizes of microemulsion droplets in equilibrium with planar adsorbed monolayers have been determined, and related to the tensions of the plane oil/aqueous phase interfaces using simple existing theory.ROBERT AVEYARD, BERNARD P. BINKS, THOMAS A. LAWLESS, et JEREMY MEAD. Can. J. Chem. 66, 000 (1988). On rapporte les tensions interfaciales des systkmes huileleau contenant un alcane pur, une solution aqueuse de chlorure de sodiumet un surfactant anionique a 1'Ctat pur: I'aCrosol OTou lep-dihexylbenzenesulphonate de sodiu-m (DHBS). On fournit des preuves qui confirment le fait que I'adsorption monocouche a I'interface huileleau peut produire des tensions trks faibles (-1 pN m-'), et qu'il n'est pas nCcessaire d'avoir a I'interface une troisikme phase riche en surfactant. On Ctudie l'aggregation du DHBS et sa repartition entre I'huile et les phases aqueuses dont on fait varier la salinitC. On confirme que dans ces conditions, compte tenu de sa structure molCculaire, le comportement du DHBS est analogue B celui de l'aCrosol OT. On a determine la taille des gouttelettes de microCmulsion en Cquilibre avec les monocouches planes adsorbees et on la relie aux tensions de l'interface plan huilelphase aqueuse en faisant appel B la thtorie existante.[Traduit par la revue]A number of studies have been made in recent years of systems which contain oil, aqueous electrolyte, and surfactant and which exhibit ultralow oillwater interfacial tensions (< lop2 mN m-'), e.g. refs. 1-7. These tensions can often be made to pass through a minimum as the temperature, electrolyte concentration, nature of the oil phase, or the concentration of a further surface-active material (e.g. cosurfactant) is varied (6-8). The minimum in tension occurs under conditions around which a surfactant-rich third or "middle" phase (intermediate in density between oil and aqueous phases) is formed. The tension between the middle phase and one of the other two ("outer") phases is lower than the oillwater tension and appears to be associated with a thick interface (3). Our concern here however is with the nature of the oillwater interface and of the surfactant aggregates which form in oil or aqueous phases at equilibrium. It has been claimed recently (9), on the basis of data obtained using sodium di-(2-ethylhexyl)sulphosuccinate (AOT) as t...

A New Family of Anionic Surfactants for Enhanced-Oil-Recovery Applications

“…These results give us confidence in our IFT experimental procedures, especially regarding how to obtain true equilibrated IFT values. Similar agreements between IFT values obtained from non-and pre-equilibrated systems were also reported by Aveyand et al (1986Aveyand et al ( , 1988. They also used a surface light-scattering technique to determine the tensions in equilibrated systems.…”

Polydispersity of AOT droplets measured by time-resolved fluorescence quenching

“…Winsor I1 microemulsions at 25 OC at different salinities from Aveyard et a1., 49 the results reported in Table I1 were obtained, with u r / i ranging between 0.138 and 0.153 for droplet sizes between?= 89and 176Awithameanof0.147. (Thesedroplets are too large for an experimental determination of the polydispersity by the fluorosecence quenching method, using PTSA as probe.)…”

Microfluidic generation and optical manipulation of ultra-low interfacial tension droplets

“…The relationship between PIT and salinity as well as the dependency of interfacial tension on salt concentration and temperature for the heptane-NaCl-water-AOT system have been characterized by Aveyard et al [13][14][15] through spinning droplet tensiometry.…”