Study of AOT-stabilized microemulsions of formamide and n-methylformamide dispersed in n-heptane

Arcoleo, V.; Aliotta, F.; Goffredi, M.; Manna, Gianfranco La; Liveri, Vincenzo Turco

doi:10.1016/s0928-4931(96)00157-9

Cited by 36 publications

(50 citation statements)

References 27 publications

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“…This is a result of the specific interactions and confined geometries. [10,18,20] For example, FTIR [10,11,18,19] and 1 H NMR [18,20] spectroscopy have shown that GY and EG interact with the AOT surfactant polar head through H-bond interactions that maintain the typical spherical reverse micelle structure but break the solvent H-bond structure present in the bulk. [6,16,18,19] Thus, even at the highest solvent loading, that is, when W S is between two and four, EG and GY show no evidence of the presence of bulklike solvent interactions inside the reverse micelles.…”

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

confidence: 99%

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

confidence: 99%

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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“…These solvents have to have high dielectric constants and very low solubility in the hydrocarbon solvents in order to form structured aggregates [8]. The most common polar solvents used include formamide (FA), dimethylformamide (DMF), dimethylacetamide (DMA), ethylene glycol (EG), propylene glycol (PG), and glycerol (GY) [9][10][11][12][13][14][15][16][17][18][19][20]. Most of these studies have been focused on phase diagrams [5], viscosity and conductivity behavior [11], and dynamic light-scattering measurements to determine micellar sizes and intermicellar interactions [12,13,15].…”

Section: Introductionmentioning

confidence: 99%

“…The most common polar solvents used include formamide (FA), dimethylformamide (DMF), dimethylacetamide (DMA), ethylene glycol (EG), propylene glycol (PG), and glycerol (GY) [9][10][11][12][13][14][15][16][17][18][19][20]. Most of these studies have been focused on phase diagrams [5], viscosity and conductivity behavior [11], and dynamic light-scattering measurements to determine micellar sizes and intermicellar interactions [12,13,15]. Also, dye absorption or emission spectra [12,[16][17][18] and FTIR [13,19,20] or 1 H NMR [19,20] spectroscopy have been used to characterize microenvironments.…”

Section: Introductionmentioning

confidence: 99%

The use of acridine orange base (AOB) as molecular probe to characterize nonaqueous AOT reverse micelles

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Biasutti

et al. 2006

Journal of Colloid and Interface Science

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“…Moreover, DMEB forms dynamical aggregates in apolar solvents capable to entrap within their chiral cores not only water but also other hydrophilic solutes as a result of the ability to form reverse micelles (a hydrophilic micellar core constituted by opportunely arranged surfactant polar heads surrounded by the surfactant hydrocarbon tails). 19,[20][21][22][23][24][25] Notably, DMEB is an ideal candidate to study the chiral recognition phenomena as well as the induced chirality in confined space. Since Schaaff and Whetten have reported optical activity in gold nanoparticles protected with L-glutathione 26 , chiral monolayer protected metal nanoclusters have attracted significant attention.…”

Section: Introductionmentioning

confidence: 99%

Induced Chirality in Confined Space on Halogen Gold Complexes

et al. 2015

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The solubilization of HAuCl4 in toluene within\ud optically active reverse micelles and lamellar structures formed\ud by (1R,2S)-Dodecyl(2-hydroxy-1-methyl-2-phenylethyl)-\ud dimethylammonium bromide (DMEB) has allowed us to\ud evidence the complex phenomenology accompanying the\ud confinement of Au salt within these nanostructures. Together\ud with a chloride/bromide exchange process occurring in the\ud first coordination sphere of an Au ion, UV−vis and electronic\ud circular dichroism (ECD) spectra reveal the appearance of an\ud induced dichroic signal attributable to Au complexes\ud entrapped in the hydrophilic domain of the DMEB chiral\ud nanostructures. Interestingly, change of the effective oxidation\ud state and coordination geometry of the gold ion confined in DMEB nanostructures has been inferred by an analysis of the Au and\ud Br X-ray Absorption Fine Spectroscopy (X-ray Absorbition Near Edge Spectroscopy and Extended X-ray Absorption Fine\ud Spectroscopy) signals. Remarkably, bromine, not covalently bonded to the organic part, acts as the vector that transfers the\ud chirality information on the DMEB to the gold complexes. Structural information on the HAuCl4 solubilized in DMEB reverse\ud micelles dispersed in toluene, obtained by SAXS, indicate the formation of elongated clusters consisting of Au complexes\ud stabilized by DMEB, confirming that the chirality transfer occurs in the micellar core of the DMEB and persists in the solid\ud composites obtained by slow evaporation of the solvent

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Study of AOT-stabilized microemulsions of formamide and n-methylformamide dispersed in n-heptane

Cited by 36 publications

References 27 publications

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

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

The use of acridine orange base (AOB) as molecular probe to characterize nonaqueous AOT reverse micelles

Induced Chirality in Confined Space on Halogen Gold Complexes

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