Interfacial Composition and Structural Parameters of Water/C₁₂-s-C₁₂·2Br/n-Hexanol/n-Heptane Microemulsions Studied by the Dilution Method

Abstract

The interfacial composition of the stable water/C12-s-C12 x 2Br/n-hexanol/n-heptane microemulsions has been studied in detail by dilution method. The results showed a marked maximum amount of the n-hexanol populating on the surfaces of droplets (represented as a = n(a)i/n(s), where n(a)i and n(s) are respectively the moles of n-hexanol and gemini surfactant on the surface of droplets) with increasing water content. At a constant level of water addition (the molar ratio of water to surfactant W0 = 20), a decreased with increasing the spacer length in the C12-s-C12 x 2Br molecule. The structural parameters of a w/o microemulsion were also estimated by analyzing the data of dilution experiments, and we found that the radius of the water pool was very sensitive to the increment of water content. The radius of the water pool varied from 0.74 to 5.35 nm with increasing W0 from 10 to 50. The variation extent reached 4.61 nm. In the cases of water/CPC/n-butanol/isopropyl myristate and water/CTAB/n-butanol/isopropyl myristate, however, the corresponding variation extents were only 1.22 and 1.68 nm, respectively, when increasing comparable water content. The ratio of N(a)/N(2C), where N(a) and N(2C) are respectively the average numbers of n-hexanol and the total average numbers of alkyl chains of gemini surfactant populating on per droplet surface, decreased obviously with increasing water content at W0 > 15. This indicated that C12-2-C12 x 2Br favored to form large droplets that were suitable to solubilize more water.

Influence of chemical architecture of oils and ionic liquid on the physicochemical and thermodynamic properties and microenvironment of anionic surfactant based microemulsion

“…In other words, association between surfactant and cosurfactant molecules at the interface becomes less favourable with increase in ω [36]. This type of variation was reported by and Paul and Nandy [36] and Zheng et al [45]. Earlier, Hait [46].…”

“…As a result, the effective packing parameter of the surfactant (P) is decreased [78,89]. From theoretical analysis, it has been observed that smaller P requires higher amount of alkanol for formation of microemulsions [45]. Hence, n a i values are found to be higher for IBB stabilized systems compared to LIM systems.…”

The Schulman Method of Cosurfactant Titration of the Oil/Water Interface (Dilution Method): A Review on a Well‐Known Powerful Technique in Interfacial Science for Characterization of Water‐in‐Oil Microemulsions

“…The concentrations of cosurfactant at the interface and in the bulk oil phase were estimated to get the distribution constant (K d ) by the dilution experiments in the light of the physicochemical rationale elaborated by Moulik and Hait [43], Bayrak [44], Mitra et al [45] and Zheng et al [39]. The total number of moles of the cosurfactant, n a present in the stable microemulsion is given by Eq.…”

“…The thermodynamic properties of microemulsion can exert significant effects on the size of nanoparticles [38]. Also, the adjustable droplet size was proposed to be useful for preparing metal nanoparticles of different sizes using W/O microemulsions as templates [39]. The above mentioned parameters were determined from this pioneering method.…”

Microemulsions: Thermodynamic and Dynamic Properties

“…www.intechopen.com During 1980s the "dilution method" was well adopted by many, to extract energetic information for different combinations along with the understanding of their structural features (Bansal et al, 1979;Birdi, 1982;Singh et al, 1993;Bayrak, 2004;Zheng et al, 2006;Zheng et al, 2007), after it was first introduced by Schulman group (Bowcott & Schulman, 1955;Schulman et al, 1959). Basically, this method deals with the estimation of distribution of cosurfactant (k d ) and hence, determines the composition of interphase which is in turn responsible for the formation and stability of microemulsions.…”