Foamability and Interfacial Rheology in Systems of Sodium Dodecyl Sulfate and Alcohols

ABSTRACT Studies were performed to assess foaming behavior in systems containing sodium dodecyl sulfate (SDS) and various alcohols. The alcohols included linear alcohols ( n = 5–12) as well as branched variants of similar carbon number. Measurements of foamability, dynamic and equilibrium surface tension, and time‐dependent dilational moduli were conducted. It was found that peaks in foamability occurred in linear systems at longer chain lengths n (greater than 10 carbons), although not exactly at n = 12. Foamability peaks additionally depended on mole fraction. Systems with branched alcohols did not exhibit peaks in foamability. Additionally, a clear correlation between surface tension and foamability was not found. Measurements of complex dilational modulus ( ε *) and elastic ( ε ′) and loss ( ε ″) components showed that complex moduli exhibited similar trends to those of the foam measurements, but did not exhibit peak values. Regions of jumps in foamability were correlated with behaviors where ε ″ > ε ′. Behaviors of foamability and moduli in linear and branched alcohol systems could be analyzed by considering the second‐order kappa shape index, a topological descriptor. It was found that peaks in foaming behavior occurred where the ratio of shape parameters for SDS and alcohol were approximately equal to 1.