Infrared spectroscopic studies on the aggregation of polyoxyethylene surfactants in hydrocarbon solvents

Abstract

Infrared spectroscopic studies have been used to determine monomer concentrations, aggregation numbers and free energies of aggregation for a series of non-ionic (polyoxyethylene ether C₁₂EO_m) surfactants in both hydrocarbon and other solvents. In n-heptane the data show that only relatively weak head group interactions occur up to about m= 6, beyond which stronger, more specific interactions begin to account for larger aggregation numbers. In apolar, but polarisable, solvents, such as benzene and CCl₄ solute–solvent interactions effectively prevent aggregation.