Reversed micelles microviscosity

The strong interactions between the water molecules also become obvious from NMR measurements by Tsujii et al..57) 13C-NMR experiments were used for determining the microviscosity of water in reversed micelles of dodecylammonium-propionate with 13C glycine cosolubilized. It was found that the apparent viscosity of the water-pool corresponds to the viscosity of a 78 % aqueous glycerol solution, obviously as a consequence of the extended network formation by strong hydrogen bonding. 

Microviscosity experiments using a molecular probe indicated a greater viscosity in micelles than in the bulk. The viscosity decreases rapidly up to go 10 and then decreases slowly as the micelle size increases. Additional studies using fluorescence probes revealed two different solvation rates inside the micelle. Zhong attributed the different solvation rates to water bound to the polar head group of AOT and bulk water inside the micelle (Zhong et al., 2002). This increased viscosity and extended solvation sphere limits the size of particles that can be synthesized using reverse micelles. 

NMR Tis) reach their minimum value. The Wo-dependence of water pool polarity (often designated micropolarity) has been investigated using solubilizated which have solvent-sensitive UV-VIS absorption spectra [59, 60] and/or solvent-sensitive fluorescent lifetimes and quantum yields [61, 62]. Fluorescence polarization decay has been used to assess microviscosities. In such studies, it is important to determine by an independent technique the solubilizate s location within the reverse micelle, so that one is certain that the probe molecule is indeed located within the water pool rather than adsorbed at the interface (i. e. at the micelle boundary). At low Wq, contact between probe and interface is of course unavoidable. Even molecules which are quite soluble in water, such as phenols, are found to bind at the interface... 

The observed rotational relaxation time of C-153 in cycloheaxne is 135 ps. In microemulsions the rotational relaxation time is bimodal in nature. The biexponential nature of rotational relaxation in TX-lOO/water reverse micelles has been reported [142,143]. Both rotational relaxation times in microemulsions are slower compared to cyclohexane. It strongly suggests that the probe molecules are residing at the core of the microemulsions. With an increase in w value the number of [BmimJlBFJ molecules increases in the core of the microemulsions, thus microviscosity also increases. The average rotational relaxation time also increases due to the increase in the viscosity of the core due to the addition of highly viscous [BmimJlBFJ. From the above discussion it is clear C-153 is located in the core of the [BmimKBFJ/TX-lOO microemulsions. 

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