ENHANCED SPREADING OF AQUEOUS FILMS CONTAINING ETHOXYLATED ALCOHOL SURFACTANTS ON SOLID SUBSTRATES

The spreading behavior of aqueous solutions containing the ethoxylated alcohol surfactants CH3(CH2)(9)(OCH2CH2)(3)OH 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 ba sis of the thermodynamic spreading coefficients calculated from static surface tensions. The data demonstrate that the spreading rates do no t depend upon any identifiable aqueous phase surfactant microstructure . However, the spreading rate dependence upon the length of the hydrop hilic poly(oxyethylene) chain suggests an interplay between surfactant adsorption on the substrate surface and the aggregation of this surfa ctant. The results suggest that the onset of turbidity, and an optimal surfactant hydrophilic/hydrophobic balance, are important for achievi ng high spreading rates.