Modification of Gibbs monolayers by chromium (III) compounds

Abstract

The present paper reveals the effects produced by a chromium (III) sulfate colloidal solution on Gibbs monolayers of (i) sodium dodecyl sulfate (SDS) and (ii) turkey red oil (TRO) formed at the air/water interface. Their intermolecular interactions and the modifications of the interphase properties play a significant role in the stabilization of concentrated reversed emulsions which have high relevance for the leather tanning technology. The changes produced in the amphiphilic monolayers were monitored employing highly sensitive surface characterization techniques such as Brewster angle microscopy (BAM), infrared reflection-absorption spectroscopy (IRRAS) and a Langmuir balance. The experimental data leads to the conclusion that amphiphile–chromium (III) complexes are formed. These complexes are characterized by an increased surface activity. In the case of the SDS containing system, the packing density increases and the hydrophobic interactions promote the formation of a stiff and brittle interface layer. Yet, only a loose packing is observed in the TRO monolayers, probably due to steric hindrance of the bulky hydrophobic chains.