Water dynamics and aggregate structure in reversed micelles at sub-zero temperatures. A deuteron spin relaxation study

Quist, Per‐Ola; Halle, Bertil

doi:10.1039/f19888401033

Cited by 54 publications

(50 citation statements)

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“…Apart from liquid solutions at room temperature the reverse micelles have recently been studied in supercritical ethane 20 and in ordinary solvents at subzero temperatures. 25 The size of the water pool increases as the ratio of the number of water molecules to that of the surfactant, w 0 , increases, and for AOT in n-heptane, the radius of the water pool (r w , in Å) is close to 2w 0 . 15b At low w 0 , the water molecules in the pool remain very close to and are very strongly attracted by the polar head groups of the surfactants and hence their mobility is very low.…”

Section: Introductionmentioning

confidence: 99%

Solvation Dynamics of Coumarin 480 in Reverse Micelles. Slow Relaxation of Water Molecules

et al. 1996

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The picosecond time-resolved Stokes shift of the laser dye coumarin 480 (I) is studied in Aerosol OT-heptane reverse micelles at various concentrations of water. On addition of water to a n-heptane solution of I containing 0.09 M AOT, the emission spectrum of I exhibits a prominent shoulder at 480 nm which is ascribed to the dye molecules in the water pool of the reverse micelles. In n-heptane, the fluorescence decays of I at short and long wavelengths are identical, which rules out any time-resolved Stokes shift. On addition of water to the AOT/heptane system, the decay at long wavelengths exhibit a distinct growth on the nanosecond time scale. This and the time-dependent Stokes shift indicate that the water molecules in the water pool of the AOT reverse micelles undergo slow relaxation on the nanosecond time scale.

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Section: Introductionmentioning

confidence: 99%

Solvation Dynamics of Coumarin 480 in Reverse Micelles. Slow Relaxation of Water Molecules

et al. 1996

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“…Techniques which have been employed to study the dynamics of water in AOT reverse micelles include ultrafast infrared (IR) spectroscopy, 3-5, 12, 15-22 nuclear magnetic resonance, 23,24 fluorescence, [25][26][27][28][29][30] neutron scattering, 31 dielectric relaxation, 32 and molecular dynamics (MD) simulations. [33][34][35] These studies collectively agree that water hydrogen bond rearrangement slows down as the reverse micelle size decreases.…”

Section: Introductionmentioning

confidence: 99%

Water dynamics in small reverse micelles in two solvents: Two-dimensional infrared vibrational echoes with two-dimensional background subtraction

Fenn¹,

Wong²,

Fayer³

2011

The Journal of Chemical Physics

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Water dynamics as reflected by the spectral diffusion of the water hydroxyl stretch were measured in w 0 = 2 (1.7 nm diameter) Aerosol-OT (AOT)/water reverse micelles in carbon tetrachloride and in isooctane solvents using ultrafast 2D IR vibrational echo spectroscopy. Orientational relaxation and population relaxation are observed for w 0 = 2, 4, and 7.5 in both solvents using IR pumpprobe measurements. It is found that the pump-probe observables are sensitive to w 0 , but not to the solvent. However, initial analysis of the vibrational echo data from the water nanopool in the reverse micelles in the isooctane solvent seems to yield different dynamics than the CCl 4 system in spite of the fact that the spectra, vibrational lifetimes, and orientational relaxation are the same in the two systems. It is found that there are beat patterns in the interferograms with isooctane as the solvent. The beats are observed from a signal generated by the AOT/isooctane system even when there is no water in the system. A beat subtraction data processing procedure does a reasonable job of removing the distortions in the isooctane data, showing that the reverse micelle dynamics are the same within experimental error regardless of whether isooctane or carbon tetrachloride is used as the organic phase. Two time scales are observed in the vibrational echo data, ∼1 and ∼10 ps. The slower component contains a significant amount of the total inhomogeneous broadening. Physical arguments indicate that there is a much slower component of spectral diffusion that is too slow to observe within the experimental window, which is limited by the OD stretch vibrational lifetime.

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“…A freezing temperature of the water core independent of the droplet size was reported as well as a strong dependency of the supercooling on the confining size. Furthermore, the dynamics of the confined water were investigated for the D 2 O/AOT/dodecane system with ω ranging from 3 to 38 from room temperature down to −43 • C [41]. The reorientation rate of the supercooled confined water was found to be 2 orders of magnitude lower than that of bulk water at the same temperature.…”

Section: Supercooling Of Water Confined In Dropletsmentioning

confidence: 96%

Aggregate Structure and Dynamic Percolation in Microemulsions

Kraska

Kuttich

Stühn

2015

Bottom-Up Self-Organization in Supramolecular Soft Matter

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This contribution deals with a special class of soft matter systems called microemulsions. They are mixtures of oil and water stabilized with a surfactant. The stabilisation is achieved through the reduction of interfacial tension by the amphiphilic surfactant. They thus consist of oil and water phases separated by a surfactant layer. The nanoscopic structure of these phases, in particular that of spherical nano droplets, is analysed in this chapter. The impact of temperature and mixing ratio of the constituents is shown. The fascinating phenomenon of dynamic droplet percolation and aggregation near a temperature induced phase separation are discussed. Microemulsions provide an excellent model system for the investigation of confinement effects on molecules. Conversely these guest molecules modify structural and dynamical properties of the microemulsion. This may even lead to the formation of transient networks with short time gel-like and long time self-diffusion dynamics of droplets.

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Water dynamics and aggregate structure in reversed micelles at sub-zero temperatures. A deuteron spin relaxation study

Cited by 54 publications

References 2 publications

Solvation Dynamics of Coumarin 480 in Reverse Micelles. Slow Relaxation of Water Molecules

Solvation Dynamics of Coumarin 480 in Reverse Micelles. Slow Relaxation of Water Molecules

Water dynamics in small reverse micelles in two solvents: Two-dimensional infrared vibrational echoes with two-dimensional background subtraction

Aggregate Structure and Dynamic Percolation in Microemulsions

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