Solubilization of Pure and Aqueous 1,2,3-Propanetriol by Reverse Aggregates of Aerosol−OT in Isooctane Probed by FTIR and ¹H NMR Spectroscopy

Abstract

Solubilization of 1,2,3-propanetriol, PT, and its aqueous solution, PT-W, (W ) water), by reverse aggregates of sodium bis(2-ethylhexyl) sulfosuccinate, Aerosol-OT or AOT, in isooctane has been studied by FTIR and 1 H NMR spectroscopy, and the results were compared with those of solubilization of 1,2ethanediol, ED, and W by the same surfactant. Curve fitting of the IR νOD band of aggregate-solubilized PT or PT-W showed the presence of a main peak and a smaller one. Dependence on [solubilizate]/[AOT] of 1 H NMR chemical shifts, δproton, of solubilized PT, PT-W, as well as the surfactant protons showed monotonic increase or decrease. Both spectroscopic techniques indicated the following order of interaction with AOT: PT > ED > W. Over the entire range of [solubilizate]/[AOT], the main νOD peak areas correspond to 88 ( 2%, and 90 ( 2% of the total peak areas for PT, and PT-W, respectively. This result shows that aggregate-solubilized PT or PT-W do not seem to coexist in "layers" of different structures, as suggested by the multistate solubilization model.

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

“…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.…”

“…To do this, we used different approaches: i) invasive techniques, such as absorption and emission spectroscopy of different molecular probes dissolved in different nonaqueous reverse micelles media, [16,17,19,28,29] and ii) noninvasive techniques, such as FTIR and 1 H NMR spectroscopy, [18,20,25] where the main effort was focused on the interpretation of the spectra of different polar solvents encapsulated inside reverse micelles to gain insights into their structure and the existence or not of a polar solvent pool. Thus, we have followed how the n OD or the n ND bands for EG, GY, PG, and FA change as the W S ratio increases.…”

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

“…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].…”

“…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. In particular, FTIR and 1 H NMR studies [19,20] have shown that, at least for EG and GY where the maximum W s (W s = [polar solvent]/[AOT]) values that can be reached are between 2 and 4, there is no evidence of the existence of bulklike solvent molecules inside the aggregates; that is, it is not possible to separate a pool from the interface.…”

Binding of o-nitroaniline to nonaqueous AOT reverse micelles

“…48 Also, the strength of this interaction is greater for GY than water. 35,37 On the other hand, EG penetrates to the lipophilic side of the interface and interacts through hydrogen bond mainly with the AOT's C=O group. Thus, EG interacts weakly with the Na + counterion which seems to be close to the AOT sulfonate group as in the case of W S = 0.…”