15min:

Q. ZHONG, D. A. STEINHURST, J. C. OWRUTSKY, Naval Research Laboratory, Code 6111, Chemistry Division, Washington DC 20375-5342.

Reverse micelles (RM) are nanosize water droplets solubilized in bulk nonpolar organic solvent by ambiphilic surfactants. Confinement effects and solvation properties can be investigated by changing the water content ( =[H₂O]/[surfactant]). FTIR spectroscopy was used to study the antisymmetric stretching vibration band of azide ion (2048.5 cm^-1 in bulk water) dissolved in nonionic nonylphenol polyoxyethylene RM as a function of . The azide band is red-shifted (compared to in bulk water) and tends toward the bulk value with increasing . The band position also depends on the charge of the surfactant. The shift with is compared with changes observed for other RM properties and is explained in terms of the water core micropolarity.