On the characterization principles of some technically important water-soluble nonionic cellulose derivatives. Part II: Surface tension and interaction with a surfactant

Abstract Some surface tension properties of aqueous solutions of eight well characterized nonionic cellulose derivatives are presented. The measurements of surface tension have been performed by the pendant drop method. Due to the initial strong time dependence of the surface tension, the measurements were performed as a function of time up to slightly less than 12 h after forming the drop. After this time there was only a very slow change in surface tension and the value after 11.7 h was taken as the apparent steady-state value of the surface tension (γ∗). The set of cellulose derivatives investigated covers a broad range in surface activity and gives values of γ∗ from 37 to 63 mN/m. The interaction of these cellulose ethers with an anionic surfactant SDS has been studied both by a fluorescence probe and a dye solubilization technique. The intensity of interaction has been expressed as the surfactant concentration where the polymer-surfactant interaction starts (CAC); the lower the value of CAC the higher is the interaction intensity. A good correlation between surface activity and hydrophobicity of the polymers as well as with the interaction intensity is shown. An approximately linear relation between surface activity of the cellulose derivatives and the CAC values is obtained.