Water Organization in Reversed Micelles

Boicelli, C. A.; Conti, Fosca; Giomini, Marcello; Giuliani, Anna Maria

doi:10.1007/978-1-4684-7538-8_11

Cited by 9 publications

(8 citation statements)

References 23 publications

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“…This picture of an inner aqueous core composed of spherical shells with different degrees of organization is in agreement with widespread investigations carried out on reverse micellar systems. 48 It is worth mentioning that we obtained analogous results using eqs 1 and 9 and the values reported in the literature for the system AOT/water/ isooctane: 35 l c ) 16 ( 2 Å and l ) 21.0 ( 0.6 Å. In this case the value d ) 5 Å is in good agreement with the thickness of the bound water layer obtained by Maitra measuring the water 1 H-NMR chemical shifts.…”

Section: Discussionsupporting

confidence: 88%

Microstructure and Dynamics of the Water-in-Oil CTAB/n-Pentanol/n-Hexane/Water Microemulsion: A Spectroscopic and Conductivity Study

et al. 1996

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Quaternary water-in-oil microemulsion of a cationic surfactant (cetyltrimethylammonium bromide, CTAB), n-hexane, water, and n-pentanol has been investigated using conductivity, quasi-elastic light scattering, nearinfrared absorption spectroscopy, and pulsed field gradient spin-echo NMR measurements. The conductivity behavior shows features characteristic of the migration of charged droplets. Consequently, using the charge fluctuation model, the conductivity data were correlated with the droplet radius obtained from self-diffusion coefficients for different obstruction factors. Conductivity and self-diffusion measurements were found to be self-consistent for spherical droplets with hard-sphere interactions. Comparison between collective diffusion and self-diffusion coefficients fully supports this conclusion. The average head-group area of CTAB, the amount of water free in the organic bulk, and the fraction of alcohol present into the aggregates were evaluated together with the thickness of both the interfacial film and the bound water layer providing a full microscopic picture of the system. IntroductionMicroemulsions are transparent, isotropic, thermodynamically stable dispersions of oil and water, stabilized by surfactant molecules. 1-3 Four-component systems of surfactant, cosurfactant (generally a short chain linear alcohol), oil, and water have many important features and are the most studied microemulsion systems. The reason for the significance of these systems is that the introduction of cosurfactant greatly extends the isotropic solution region, especially with single-chain ionic surfactants. Microemulsions based on the cationic surfactant cetyltrimethylammonium bromide (CTAB) have been extensively used as host for different enzymes. 4 These systems offer the possibility to compare the enzymatic activities performed in a cationic microemulsion with those performed in the wellknown systems AOT/hydrocarbon/water. 5 Furthermore, the system CTAB/n-pentanol/n-hexane/water can be a useful tool to investigate the properties of anionic polyelectrolytes such as nucleic acids, 6 since the system is cationic, is transparent in the UV region (avoiding the limitation imposed by the use of chloroform which is often employed as cosolvent for CTABbased microemulsions 7 ), and can solubilize high quantities of water, up to 80 molecules of water per surfactant molecule. These characteristics are at the basis of two recent papers, where this microemulsion was used as a microreactor to perform the self-replication of oligonucleotides. 8,9 Despite such widespread interest in CTAB water-in-oil (w/ o) microemulsions, little is known about their microstructure. This prevents one from completely understanding the basic mechanism of the phenomena taking place inside them. The problem of the structure of a quaternary microemulsion is not an easy task to afford, as can be deduced by the fact that several studies, making use of a wide range of experimental techniques, gave a small contribution toward a reliable picture of these syst...

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Section: Discussionsupporting

confidence: 88%

Microstructure and Dynamics of the Water-in-Oil CTAB/n-Pentanol/n-Hexane/Water Microemulsion: A Spectroscopic and Conductivity Study

et al. 1996

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“…The W 0,P values obtained are similar to the reported values for phospholipid hydration in benzene as obtained by 1 H-NMR and infrared analysis (2,28). In these latter studies (28), it was found that the first hydration shell of phospholipids was formed by 9-11 water molecules.…”

Section: Comparison With Other Systemssupporting

confidence: 87%

Reverse Micelle Systems Composed of Water, Triton X-100, and Phospholipids in Organic Solvents

Rodrı́guez

Vargas

Fernández‐Velasco

1998

Journal of Colloid and Interface Science

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“…This is significant because our results are compared to FTIR and NMR techniques that do not require a probe molecule. Furthermore, some solutes present in the micellar interior have been shown to redistribute water organization . However, C343 and related coumarins are not reported to have specific interactions with water…”

Section: Discussionmentioning

confidence: 99%

“…In this role, it can be used to deliver pharmaceuticals and cosmetics and is preferable to bioincompatible surfactants such as AOT . Direct comparison between lecithin reverse micelles and lipid bilayers can be drawn since the water-headgroup interactions should be very similar , Current theory juxtaposes the static properties of the transient network to semidilute solutions of flexible polymers, , hence the term “living polymers”.…”

Section: Introductionmentioning

confidence: 99%

Dynamics of Polar Solvation in Lecithin/Water/Cyclohexane Reverse Micelles

1998

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The solvation dynamics of water in lecithin/cyclohexane reverse micelles have been determined via ultrafast time-resolved fluorescence studies. At hydration levels w 0 ≤ 4.8, the reverse micellar samples are nonviscous. Here a single relaxation time is observed that is much longer than the response of free or bulk water. In contrast, small additions of water to the samples produces a viscous gel, referred to by others as an organogel or “living polymer”. At hydration levels of w 0 ≥ 5.8, three relaxation times are observed with approximate time constants of 0.5, 15, and 200 ps, the shortest of which correlates to free water motion. The dynamics reveal no evidence of micelle crossover or branch points associated with gel formation. In comparison to Aerosol OT reverse micelles of similar hydration, the water in the lecithin reverse micelles is significantly more restricted. It is proposed that lecithin sequesters significantly more water than previously predicted precluding formation of distinct core water pools in the micelles. The results are also compared to models for aqueous structure and dynamics near phospholipid membranes and to bulk water dynamics.

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Water Organization in Reversed Micelles

Cited by 9 publications

References 23 publications

Microstructure and Dynamics of the Water-in-Oil CTAB/n-Pentanol/n-Hexane/Water Microemulsion: A Spectroscopic and Conductivity Study

Microstructure and Dynamics of the Water-in-Oil CTAB/n-Pentanol/n-Hexane/Water Microemulsion: A Spectroscopic and Conductivity Study

Reverse Micelle Systems Composed of Water, Triton X-100, and Phospholipids in Organic Solvents

Dynamics of Polar Solvation in Lecithin/Water/Cyclohexane Reverse Micelles

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