Role of the Succinate Skeleton in the Disorder–Order Transition of AOT and Its Analogous Molecules: Detection by Infrared Absorption Spectra of the Configurations Arising from the Difference in Torsion Angles of the Succinate Skeleton

Abstract

Abstract The IR spectra in the 1300–1450 cm−1 region, which reflect the CH and CH2 deformation vibrational modes of the succinate skeleton, have been investigated in detail for sodium dialkylsulfonates (alkyl groups: ethyl, n-propyl, n-butyl, n-hexyl, n-heptyl, n-octyl, n-decyl, and n-dodecyl) and sodium 1,2-bis(2-ethylhexyl)sulfosuccinate (sodium 1,2-bis(2-ethylhexyloxycarbonyl)ethanesulfonate) (AOT). The results have provided clear evidence that two configurations, arising from the difference in the torsion angles of the succinate skeleton, are preferentially stabilized in aqueous solution as well as in the solid state, depending upon the concentration. Thus, the IR spectra of this region can be used as a powerful tool for elucidation of the mechanism of the disorder–order transition in aggregate systems of AOT or its homologs at the molecular level.