A Study of AOT Reverse Micelles in Liquids at Ambient and High Pressure

Giddings, Luther D.; Olesik, Susan V.

doi:10.1021/la00021a008

Cited by 19 publications

(16 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A clear differentiation between 1‐butanol and 2‐butanol isomers was also found using AOT aggregates in CDCl 3 for six samples containing 47 m m of each isomer, varying the concentration of AOT from 24 to 428 m m . All six samples were well above the cmc values reported for AOT in chloroform . The diffusion coefficients for butanol isomers are plotted as a function of AOT concentration in Fig.…”

Section: Resultssupporting

confidence: 69%

“…The effect of AOT concentration on the diffusion of the methoxyphenol isomers was investigated using six samples containing 20 m m of each of the three isomers, varying the concentration of AOT from 52 to 310 m m . All six samples were well above the two cmc values reported previously for AOT in chloroform (0.8 m m obtained by both UV and NMR, and 6.5 m m by NMR). The diffusion coefficients for the methoxyphenol isomers are plotted as a function of AOT concentration in Fig.…”

Section: Resultsmentioning

confidence: 78%

“…All six samples were well above the cmc values reported for AOT in chloroform. [49,50] The diffusion coefficients for butanol isomers are plotted as a function of AOT concentration in Fig. 3(b).…”

Section: In Such a Model The Bound [A] B /[A] 0 And Free [A] F /[A] mentioning

confidence: 99%

See 2 more Smart Citations

Matrix‐assisted diffusion‐ordered spectroscopy: application of surfactant solutions to the resolution of isomer spectra

Tormena

Evans

Haiber

et al. 2012

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

The component spectra of a mixture of isomers with nearly identical diffusion coefficients cannot normally be distinguished in a standard diffusion-ordered spectroscopy (DOSY) experiment but can often be easily resolved using matrix-assisted DOSY, in which diffusion behaviour is manipulated by the addition of a co-solute such as a surfactant. Relatively little is currently known about the conditions required for such a separation, for example, how the choice between normal and reverse micelles affects separation or how the isomer structures themselves affect the resolution. The aim of this study was to explore the application of sodium dodecyl sulfate (SDS) normal micelles in aqueous solution and sodium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT) aggregates in chloroform, at a range of concentrations, to the diffusion resolution of some simple model sets of isomers such as monomethoxyphenols and short chain alcohols. It is shown that SDS micelles offer better resolution where these isomers differ in the position of a hydroxyl group, whereas AOT aggregates are more effective for isomers differing in the position of a methyl group. For both the normal SDS micelles and the less well-defined AOT aggregates, differences in the resolution of the isomers can in part be rationalised in terms of differing degrees of hydrophobicity, amphiphilicity and steric effects.

show abstract

Section: Resultssupporting

confidence: 69%

Section: Resultsmentioning

confidence: 78%

See 1 more Smart Citation

Matrix‐assisted diffusion‐ordered spectroscopy: application of surfactant solutions to the resolution of isomer spectra

Tormena

Evans

Haiber

et al. 2012

Magnetic Reson in Chemistry

View full text Add to dashboard Cite

show abstract

“…Some authors add water or other polar solvents to enable the measurement of properties of inverse micelles; however, as stated above, the presence of water can impact the formation of inverse micelles. [79][80][81][82][83] Although the addition of water does enable the formation of inverse micelles, such samples would be more accurately be described as microemulsions. In this review, systems with a minimal amount of water are considered so that charging will arise from inverse micelles rather than microemulsions.…”

Section: Inverse Micellesmentioning

confidence: 99%

“…Of the additives used in charging studies, AOT is the most commonly studied surfactant. CMCs have been measured using techniques including solubilization of an optically active probe particle, 82,97-100 light scattering, 71,101 titration calorimetry, 98 interfacial tension with mercury, 102 positron annihilation, 103 NMR, 81 water solubilization, 80 and SANS. 95,104 The CMC of OLOA surfactant has been studied using optical probe particles 99,105,106 and transient current measurements.…”

Section: Inverse Micellesmentioning

confidence: 99%

Controlling colloid charge in nonpolar liquids with surfactants

Smith

Eastoe

2013

Phys. Chem. Chem. Phys.

100

146

View full text Add to dashboard Cite

The formation of ions in nonpolar solvents (with relative permittivity ε r of approximately 2) is more difficult than in polar liquids; however, these charged species play an important role in many applications, such as electrophoretic displays. The low permittivities (ε r) of these solvents mean that charges have to be separated by large distances to be stable (approximately 28 nm or 40 times that in water). The inverse micelles formed by surfactants in these solvents provide an environment to stabilize ions and charges. Common surfactants used are sodium dioctylsulfosuccinate (Aerosol OT or AOT), polyisobutylene succinimide, sorbitan oleate, and zirconyl 2-ethyl hexanoate. The behavior of charged inverse micelles has been studied on both the bulk and on the microscopic scale and can be used to determine the motion of the micelles, their structure, and the nature of the electrostatic double layer. Colloidal particles are only weakly charged in the absence of surfactant, but in the presence of surfactants, many types, including polymers, metal oxides, carbon blacks, and pigments, have been observed to become positively or negatively charged. Several mechanisms have been proposed as the origin of surface charge, including acid-base reactions between the colloid and the inverse micelle, preferential adsorption of charged inverse micelles, or dissolution of surface species. While most studies vary only the concentration of surfactant, systematic variation of the particle surface chemistry or the surfactant structure have provided insight into the origin of charging in nonpolar liquids. By carefully varying system parameters and working to understand the interactions between surfactants and colloidal surfaces, further advances will be made leading to better understanding of the origin of charge and to the development of more effective surfactants.

show abstract