A Fourier Transform Infrared Study on the Structure of Water Solubilized by Reverse Aggregates of Sodium and Magnesium Bis(2-ethylhexyl)sulfosuccinates in Organic Solvents
✍ Scribed by Luzia P. Novaki; Omar A.El Seoud
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 240 KB
- Volume
- 202
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
chemical and enzymatic reactions and preparation of poly-The structure of water (4% D 2 O in H 2 O, v/v) solubilized by mers and quasi-monodisperse inorganic particles (1-8). the reverse aggregates of sodium bis(2-ethylhexyl) sulfosuccinate It is important to understand fully the properties of water [Na(AOT)] in heptane and by magnesium bis(2-ethylhexyl) sulsolubilized by surfactant aggregates in organic solvents befosuccinate [Mg(AOT) 2 ] in toluene has been probed by FT-IR. cause of the participation of water in hydration of the surfac-The n OD band of solubilized HOD has been recorded as a function tant headgroup and, when the surfactant is used as a catalyst, of the [water]/[surfactant] molar ratio, W/S, up to the phase in solvation of reactants, transition states, and proton transseparation boundary for Na(AOT), W/S of 60, and to W/S of 33 fers. The [water]/[surfactant] molar ratio (W/S) 2 is usually for Mg(AOT) 2 . Curve-fitting of this band showed the presence of used to designate the aggregates present in solution, either main peaks at 2530 { 19 and 2523 { 7 cm 01 , and small peaks at 2355 { 43 and 2352 { 18 cm 01 for Na(AOT) and Mg(AOT) 2 , as wet reverse micelles (RMs) or as W/O mE.
In RMs the respectively. Over the entire W/S range, the main peak correamount of solubilized water is smaller than or equal to the sponds to 92 { 3% (Na(AOT)) and 92 { 2% (Mg(AOT) 2 ) of the amount necessary to hydrate the surfactant headgroup. Solutotal peak area. For each surfactant, as a function of increasing bilization of water beyond this W/S results in the formation W/S, the frequency of the main peak decreases, whereas its full of a W/O mE (1-3).
width at half-height increases; values of both properties at W/S
An important aspect of solubilized water is the physicoof 60 for Na(AOT) and at W/S of 33 for Mg(AOT) 2 are close to chemical model that describes its state. In the multi-state the corresponding ones for HOD in bulk aqueous phase. These model, water is pictured as coexisting in ''states,'' or ''layresults show that the aggregate-solubilized water, although differers.'' One layer is at the periphery of the micellar water ent from bulk water, does not seem to coexist in ''layers'' of differ-''pool'' and is made of water molecules strongly bound to the ent structures, as suggested by the multistate water solubilization surfactant headgroup, W bound . Properties of this water deviate model.