Solvation and Ordered Structures in Reversed Micelles

Molecules consisting of polar and apolar moieties behave as amphiphiles they are simultaneously hydro- and lipophilic or hydrophilic and hydrophobic. Due to this 

Micelles and reversed micelles are able to solubilize substances which are insoluble in the bulk phase of the system considered. This solubilization is due to a solvation by the amphiphile and concomitantly a change in the order of the solubilized molecules may occur as a consequence of its modified solvation shell. In this sense reversed micelles of detergents in hydrophobic solvents with solubilized water in the core are 

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. 

Similar conclusions were obtained from lH and 31P NMR and also from IR studies of egg phospholecithin reversed micelles in benzene by Boicelli et al. 58 61). According to the results of these experiments the water structure within the reversed phospholecithin micelles alters considerably compared with water in bulk. This becomes evident from the shortening of the relaxation time T, of the water protons split into two relaxation times T1A and T1B, indicating that there are at least two 

With increasing water content the reversed micelles change via swollen micelles 62) into a lamellar crystalline phase, because only a limited number of water molecules may be entrapped in a reversed micelle at a distinct surfactant concentration. Tama-mushi and Watanabe 62) have studied the formation of reversed micelles and the transition into liquid crystalline structures under thermodynamic and kinetic aspects for AOT/isooctane/water at 25 °C. According to the phase-diagram, liquid crystalline phases occur above 50—60% H20. The temperature dependence of these phase transitions have been studied by Kunieda and Shinoda 63). 

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