Structures of metal bis(2-ethylhexylsulfosuccinate) aggregates in cyclohexane

Eastoe, Julian; Towey, Tom F.; Robinson, Brian H.; Williams, Jason A.; Heenan, Richard K.

doi:10.1021/j100109a035

Cited by 129 publications

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“…The counterions were exchanged using previously published methods (47), with the surfactants and counterion identities verified using 1 H NMR and 23 Na NMR. Reverse nanoemulsions were made by dissolving enough M:AOT (M = Na + , K + , and Mg 2+ ) in CCl 4 to create a 1 mM AOT concentration and sonicated with a 1% aqueous phase.…”

Section: Orientation and Solvation Of The Aot Head Groupmentioning

confidence: 99%

Molecular characterization of water and surfactant AOT at nanoemulsion surfaces

Hensel

Carpenter

Ciszewski

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Nanoemulsions and microemulsions are environments where oil and water can be solubilized in one another to provide a unique platform for many different biological and industrial applications. Nanoemulsions, unlike microemulsions, have seen little work done to characterize molecular interactions at their surfaces. This study provides a detailed investigation of the near-surface molecular structure of regular (oil in water) and reverse (water in oil) nanoemulsions stabilized with the surfactant dioctyl sodium sulfosuccinate (AOT). Vibrational sum-frequency scattering spectroscopy (VSFSS) is used to measure the vibrational spectroscopy of these AOT stabilized regular and reverse nanoemulsions. Complementary studies of AOT adsorbed at the planar oil-water interface are conducted with vibrational sum-frequency spectroscopy (VSFS). Jointly, these give comparative insights into the orientation of interfacial water and the molecular characterization of the hydrophobic and hydrophilic regions of AOT at the different oil-water interfaces. Whereas the polar region of AOT and surrounding interfacial water molecules display nearly identical behavior at both the planar and droplet interface, there is a clear difference in hydrophobic chain ordering even when possible surface concentration differences are taken into account. This chain ordering is found to be invariant as the nanodroplets grow by Ostwald ripening and also with substitution of different counterions (Na:AOT, K:AOT, and Mg:AOT) that consequently also result in different sized nanoparticles. The results paint a compelling picture of surfactant assembly at these relatively large nanoemulsion surfaces and allow for an important comparison of AOT at smaller micellar (curved) and planar oil-water interfaces.nanoemulsions | oil-water interfaces | vibrational sum-frequency scattering spectroscopy | surface spectroscopy | surfactants W e are all familiar with the adage that "oil and water do not mix," but of course, it depends upon the definition of "mix." Emulsions are an important special case, where the oil is dispersed as tiny droplets in the aqueous phase, taxonomically called a regular emulsion, or where the water is dispersed as tiny droplets throughout the oil phase, called a reverse emulsion. Because both emulsions are thermodynamically unstable, overcoming this requires an emulsifying agent such as a surfactant. Recently, there has been interest in surfactant-stabilized emulsions with droplet diameters in the nanoscale range for unique applications in drug delivery (1, 2) and oil recovery (3, 4) and as nanoreactors to produce materials ranging from polymers to quantum dots (5). Regular or reverse emulsions with droplet diameters in the range of 10-1,000 nm are called nanoemulsions. Little is known about the processes or molecular structures that result in their stability via surfactants. Even less is known about the structure-function relationship, which is crucial to determine the best surfactant for a given nanoemulsion application. Their utility hinges on a ...

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Section: Orientation and Solvation Of The Aot Head Groupmentioning

confidence: 99%

Molecular characterization of water and surfactant AOT at nanoemulsion surfaces

Hensel

Carpenter

Ciszewski

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…The larger bilayer thickness for TPA-iC18S(FO-180) surfactants is consistent and in line with increased counterion size, which demonstrates that ion association can be detected for these single chain surfactants, in contrast to single chain DS surfactants. 21 Although it has been shown previously that counterion nature can strongly affect the shape of the aggregates, 21,57 interestingly, counterion size and shape does not significantly influence the shape of the high Q, however, the origin of the scattering at low Q is likely to be residual lamellar fragments. synthesized with the intention of pushing the "hedgehog" molecules to the limit of reducing surface energy.…”

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confidence: 90%

Low-Surface Energy Surfactants with Branched Hydrocarbon Architectures

et al. 2014

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“…In systems of mixed surfactants and hydrotropes of the same charge the electrostatic repulsion diminishes interfacial co-adsorption. Elongated microemulsions were discovered by Petit [13] and Eastoe et al [14][15][16] who first observed cylindrical or ellipsoidal reverse microemulsions with the Aerosol-OT (AOT) anion coupled with Cobalt counterions (substituted for the normally found Sodium ion). This work was taken further to explore the effects of different metal counterions on AOT microemulsion morphology [14][15][16], and recently showing elongated self-assembly structures in supercritical CO2 with related surfactants [17].…”

Section: Introductionmentioning

confidence: 99%

Effects of small ionic amphiphilic additives on reverse microemulsion morphology

Hatzopoulos

James

Rogers

et al. 2014

Journal of Colloid and Interface Science

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General rightsThis document is made available in accordance with publisher policies. Please cite only the published version using the reference above. Full terms of use are available: http://www.bristol.ac.uk/pure/about/ebr-terms Effects of small ionic amphiphilic additives on reverse microemulsion morphology Research Highlights Cylindrical morphologies of reverse microemulsions induced by small molecule hydrotropes.  Ellipsoidal droplets of high aspect ratio in reverse AOT microemulsions are induced by short chain alkanoate additives.  A cylinder to sphere transition in reverse AOT microemulsions is seen with increasing water content. . Microemulsion domain structures were investigated by small-angle neutron scattering (SANS), and these data were fitted by structural models to yield information on the shapes (spheres, ellipsoids or cylinders) and sizes of the nanodroplets. Effects of small ionic amphiphilic additives on reverse microemulsion morphology FindingsUnder the conditions of study hydrotrope chemical structure has a significant effect on microemulsion structure: sodium cyclohexanoate does not induce the formation of cylindrical/ellipsoidal nanodroplets, whereas the aromatic analogue sodium benzoate does. Furthermore, the short chain sodium hexanoate does not cause anisotropic microemulsions, but the more hydrophobic longer chain heptanoate and octanoate analogues do induce sphere-to-ellipsoid transitions. This study shows that underlying microemulsion structures can be tuned by hydrotropes, and that the strength of the effect can be identified with hydrotrope hydrophobicity in terms of the bulk aqueous phase cac.

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Structures of metal bis(2-ethylhexylsulfosuccinate) aggregates in cyclohexane

Cited by 129 publications

References 0 publications

Molecular characterization of water and surfactant AOT at nanoemulsion surfaces

Molecular characterization of water and surfactant AOT at nanoemulsion surfaces

Low-Surface Energy Surfactants with Branched Hydrocarbon Architectures

Effects of small ionic amphiphilic additives on reverse microemulsion morphology

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