Investigation of self-assembled surfactant structures at the solid-liquid interface using FT-IR/ATR

The structure of self-assembled surfactant films at the solid/liquid interf ace is investigated using Fourier transform infrared spectroscopy/attenuate d total internal reflection spectroscopy (FT-IR/ATR) techniques, to underst and the structural transitions taking place at the interface. The structura l transitions, as determined from the ATR technique, are correlated to the change in interfacial properties, such as contact angle and zeta potential, and the presence/absence of steric repulsive barriers in the presence of s urfactants at the interface. A transition to randomly oriented self-assembl ed spherical aggregates appears to take place at concentrations below the b ulk critical micelle concentration, directly from hemi-micelles, without th e formation of bilayers. The onset of steric repulsive forces in the presen ce of surfactants was found to occur within the same concentration range, w here the transition of the interface structure to predominantly spherical a ggregates occurs.