Relationship between air-water interfacial dilational viscoelasticity and foam property in aqueous solutions of sodium alkylsulfates with different hydrocarbon chains

The influence of alkyl chain structures in sodium alkylsulfates (ASs) on their rheological properties was investigated in this study. Dilational viscoelasticity at the air-water interface, dynamic surface tension, and foam property were quantitatively evaluated in aqueous solutions of ASs with different hydrocarbon chains, and the relationship was systematically discussed. The experimental results show that the alkyl chain plays an important role in the interfacial dilational properties. For ASs with straight alkyl chains, AS with the longer alkyl chain showed the maximum value of the interfacial dilational viscoelasticity at the lower concentration. The longer the alkyl chain of AS was the larger the maximum value of the interfacial dilational viscoelasticity was. The frequency dependence of the interfacial dilational viscoelasticity was confirmed only in the range of high surfactant concentrations, suggesting that the interfacial relaxation process is mainly controlled by the diffusion of the surfactants. As for the relationship between interfacial dilational viscoelasticity and foam property, it was found that the maximum value of the interfacial dilational viscoelasticity was correlated with the foam stability under the conditions.