FT-IR studies on the conformation and effective head-group area of AOT molecules in W/O microemulsions

Abstract

Using Fourier transform infrared(FT-IR) spectroscopy technique, the carbonyl stretching vibration bands of AOT in sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/isooctane/water reverse (W/O) microemulsions system have been investigated by least square curve fitting. The results indicate that an asymmetric adsorbed peak of carbonyl stretching vibration of AOT molecule is situated in (1739 ± 1) and (1725 ± 2) cm -1 . The two peaks correspond to different carbonyls in gauche conformation and trans conformation of AOT molecules, respectively. With different water contents ( W 0 ), the variations of peak intensity ratio ( I r1 = I 1739 / I 1725 ) reflect the change of the ratio for the two conformation populations and the variations of the effective head-group area of AOT molecule have relations to the ratio of two conformation populations.