Enhanced Spreading of Aqueous Films Containing Ethoxylated Alcohol Surfactants on Solid Substrates

Abstract

The spreading behavior of aqueous solutions containing the ethoxylated alcohol surfactants CH3(CH2)9(OCH2CH2)3OH and CH3(CH2)11(OCH2)n−OH (n = 3−6) on solid substrates has been investigated at different surfactant concentrations and substrate surface energies. The trends in the dynamic spreading behavior differ from those expected on the basis of the thermodynamic spreading coefficients calculated from static surface tensions. The data demonstrate that the spreading rates do not depend upon any identifiable aqueous phase surfactant microstructure. However, the spreading rate dependence upon the length of the hydrophilic poly(oxyethylene) chain suggests an interplay between surfactant adsorption on the substrate surface and the aggregation of this surfactant. The results suggest that the onset of turbidity, and an optimal surfactant hydrophilic/hydrophobic balance, are important for achieving high spreading rates.