A Fourier transform infrared study of water—head group interactions in reversed micelles containing sodium bis(2-ethylhexyl) sulfosuccinate (AOT)

Christopher, David J; Yarwood, J.; Belton, Peter; Hills, B.P.

doi:10.1016/0021-9797(92)90047-p

Cited by 119 publications

(155 citation statements)

References 45 publications

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“…It can be noted that, after an initial rapid decrease, the f * value trends to a plateau. This behavior is similar to that shown by cyanamide when it is confined within AOT reverse micelles and similarly it makes possible to state that solubilizate/surfactant interactions mainly occur between the OH group of DDT or DLT and the SO 3 − surfactant ionic head groups tending to the complete saturation at the higher R [8,17]. Fig.…”

Section: Aot So 3 − Stretching Bandsupporting

confidence: 80%

Confinement of chiral molecules in reverse micelles: FT-IR, polarimetric and VCD investigation on the state of dimethyl tartrate in sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles dispersed in carbon tetrachloride

Abbate

Longhi

Ruggirello

et al. 2008

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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a b s t r a c tThe state of d and l-dimethyl tartrate confined within dry sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles dispersed in CCl 4 has been investigated by FT-IR spectroscopy, polarimetry, and vibrational circular dichroism (VCD). Measurements have been performed at 25 • C as a function of the solubilizate-to-surfactant molar ratio (R) at a fixed AOT concentration (0.158 M). The analysis of experimental data is consistent with the hypothesis that both enantiomers of dimethyl tartrate are mainly entrapped in the reverse micelles and located in proximity to the surfactant head-group region. The formation of this interesting self-organized chiral nanostructure involves some changes of the typical H-bonding of dimethyl tartrates in the pure solid state or as monomers dispersed in CCl 4 attributable to the establishment of specific solubilizate/surfactant head-group interactions and confinement effects.

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Section: Aot So 3 − Stretching Bandsupporting

confidence: 80%

Confinement of chiral molecules in reverse micelles: FT-IR, polarimetric and VCD investigation on the state of dimethyl tartrate in sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles dispersed in carbon tetrachloride

Abbate

Longhi

Ruggirello

et al. 2008

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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“…However, when water [33] or EG or GY (Figure 2) are encapsulated inside reverse micelles, the 1720 cm À1 band does not decrease as it is expected for a rotamer equilibrium shift. So, it seems that other factors are affecting the AOT C=O asymmetric band.…”

mentioning

confidence: 78%

“…Few reports deal with the investigation of the vibrational modes associated with the sulfonate and the ester moieties of the AOT head group upon water encapsulation, although meaningful information can be obtained from these modes. [25,[31][32][33] On the other hand, there are no reports in the literature about the investigation of the AOT modes for nonaqueous reverse micelles, except for FA. [25] Moreover, we show here that FTIR spectroscopy is a very powerful technique because not only the frequency band shifts can be monitored but also the band intensity.…”

Section: [Water]/a C H T U N G T R E N N U N G [Aot] = 10 (Aqueous) Wmentioning

confidence: 94%

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Effect of the Constrained Environment on the Interactions between the Surfactant and Different Polar Solvents Encapsulated within AOT Reverse Micelles

et al. 2009

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Herein, we report a study of the interactions between different nonaqueous polar solvents, namely, ethylene glycol (EG), propylene glycol (PG), glycerol (GY), dimethylformamide (DMF), and dimethylacetamide (DMA), and the polar heads of sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) in nonaqueous AOT/n-heptane reverse micelles. The goal of our study is to gain insights into the unique reverse-micelle microenvironment created upon encapsulation of these polar solvents. For the first time, the study is focused on determining which regions of the AOT molecular structure are involved in the interactions with the polar solvents. We use FTIR spectroscopy--a noninvasive technique--to follow the changes in the AOT C=O band and the symmetric and asymmetric SO(3)(-) vibration modes upon increasing the content of polar solvents in the micelles. The results show that GY interacts through H bonds with the SO(3)(-) group, thereby removing the Na(+) counterions from the interface remaining in the polar core of the micelles. PG and EG interact through H bonds, mainly with the C=O group of AOT, penetrating into the oil side of the interface. Thus, they interact weakly with the Na(+) counterion, which seems to be close to the AOT sulfonate group. Finally, DMF and DMA, encapsulated inside the reverse micelles, interact neither with the C=O nor with the SO(3)(-) groups, but their weakly bulk-associated structure is broken because of the interactions with Na(+). We suggest that DMF and DMA can complex the Na(+) ions through their carbonyl and nitrogen groups. Hence, our results do not only give insights into how the constrained environment affects the bulk properties of polar solvents encapsulated within reverse micelles but--more importantly--they also help us to answer the tricky question about which regions of the AOT moiety are involved in the interactions with the polar solvents. We believe that our results show a clear picture of the interactions present at the nonaqueous reverse-micelle interface; this is important because these media are interesting nanoreactors for heterogeneous chemistry, templates for nanoparticles, and models for membranes.

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“…As one of the several advantages of a reverse AOT micellar system, the size of the water pool can be controlled precisely at the nanometer level through the molar ratio of water to AOT: 7 Therefore, size effects on chemical and physical properties in nanometer dimensions can be studied by the use of reverse AOT micelles. Indeed, reverse AOT micelles have been studied by various techniques such as fluorescence spectroscopy [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] , NMR 22,23 , ESR 24,25 , IR [26][27][28] , and so on. [29][30][31][32] These studies demonstrated that polarity [8][9][10] , viscosity 11 , pH 12 , and other properties 30,32 of the water pool in the micelles were different from those in the bulk state and were dependent on the w 0 value.…”

mentioning

confidence: 99%

Energy Gap Dependence of the Nonradiative Decay Rate Constant of 1-Anilino-8-naphthalene Sulfonate in Reverse Micelles

et al. 1999

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Spectroscopic or electrochemical analysis of a solute(s) confined in a minute volume is one of the promising approaches toward ultratrace analyses. Recent advances in various microspectroscopies and highly sensitive detection techniques have provided such new analytical methods. Furthermore, these techniques have revealed characteristics of chemical and physical phenomena in minute dimensions. As an example, our group reported previously that the rates of electron transfer and mass transfer across single microdroplet/water interfaces depended on the size of the droplet, as demonstrated by a laser trapping-spectroscopy-electrochemistry method. 1-4 Molecular association of a dye in individual micrometer-sized water droplets was also shown to be facilitated by decreasing the droplet size. 5,6 These size effects are observed owing to an increase in the surface area/volume (A/V) ratio of a droplet as the size decreases. Actually, the droplet size effects mentioned above (droplet diameter (d )>10 µm) were explained in terms of a change in the A/V ratio of the droplet. 2 For droplets with d<10 µm, on the other hand, other characteristic droplet size effects, caused by a change in droplet/solution interfacial structures or by thermal fluctuations of the interface, have been observed. 3,4 Clearly, the roles of a surface or interface in determining chemical and physical characteristics of a droplet become important as the size decreases. In submicrometer -nanometer dimensions, therefore, more pronounced size effects are expected. At the present stage of our investigation, however, a droplet size studied by the laser trappingspectroscopy-electrochemistry technique is limited to d>2 µm. In order to obtain knowledge which would bridge characteristic behavior in micrometer and in nanometer dimensions, experimental approaches other than the laser trapping method are necessary.As a system comprised of nanometer-sized droplets, reverse micellar systems have attracted broad interests, these are the systems in which water droplets (or water pools) are surrounded by surfactant molecules and an oil phase. 7 In particular, reverse AOT (sodium bis(2-ethylhexyl)sulfosuccinate) micelles have been studied extensively during the past decades.7-32 As one of the several advantages of a reverse AOT micellar system, the size of the water pool can be controlled precisely at the nanometer level through the molar ratio of water to AOT: w 0 =[H 2 O]/[AOT]. 7 Therefore, size effects on chemical and physical properties in nanometer dimensions can be studied by the use of reverse AOT micelles. Indeed, reverse AOT micelles have been studied by various techniques such as fluorescence spectroscopy 7-21 , NMR 22,23 , ESR 24,25 , , and so on. [29][30][31][32] These studies demonstrated that polarity 8-10 , viscosity 11 , pH 12 , and other properties 30,32 of the water pool in the micelles were different from those in the bulk state and were dependent on the w 0 value. In addition to such characteristics, since reverse AOT micelles have been utilized wide...

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A Fourier transform infrared study of water—head group interactions in reversed micelles containing sodium bis(2-ethylhexyl) sulfosuccinate (AOT)

Cited by 119 publications

References 45 publications

Confinement of chiral molecules in reverse micelles: FT-IR, polarimetric and VCD investigation on the state of dimethyl tartrate in sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles dispersed in carbon tetrachloride

Confinement of chiral molecules in reverse micelles: FT-IR, polarimetric and VCD investigation on the state of dimethyl tartrate in sodium bis(2-ethylhexyl) sulfosuccinate reverse micelles dispersed in carbon tetrachloride

Effect of the Constrained Environment on the Interactions between the Surfactant and Different Polar Solvents Encapsulated within AOT Reverse Micelles

Energy Gap Dependence of the Nonradiative Decay Rate Constant of 1-Anilino-8-naphthalene Sulfonate in Reverse Micelles

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