Separation of Bulk and Interfacial FTIR Absorption Spectra for H2O/AOT/Isooctane Reverse Micelles (38 ≤ w0 ≤ 60) by Volumetric Analysis of the OH Stretching Band of Water

FTIR absorption spectra of H2O/AOT/isooctane reverse micelles (38 ≤ w0 ≤ 60) were measured and analyzed by volumetric analysis of the OH stretching band of water (~3000 – 3800 cm-1). Dynamic light scattering and density measurements were also made. A value of interfacial depth could not be obtained, but interfacial and bulk spectral responses were obtained by holding the interfacial depth constant at 0.45 nm. A scaled, normalized FTIR absorption spectrum of pure liquid water was subtracted from the normalized reverse micelle absorption spectra as another means of obtaining the interfacial spectrum. For both of these methods it was found that the interfacial spectrum, but not the bulk spectrum, is sensitive to changes in the value of AOT tail length utilized. The interfacial spectra obtained using tail lengths between 1 and 2 nm are virtually identical to those obtained by past researchers using reverse micelles with w0 ≤ 21