Models of Two-Dimensional Solution Assuming the Internal Compressibility of Adsorbed Molecules: A Comparative Analysis

The description of surface dilational rheology data by theoretical models has some general problems, essentially in the range of larger surface coverage. Typically, the dilational elasticity calculated from theoretical models increases with surfactant bulk concentration and reaches values so far not observed in any experiment. In contrast, the experimental elasticities in the high-frequency limit show an increase with concentration followed by a plateau or flat maximum. Various thermodynamic models for the state of interfacial layers are discussed with respect to the corresponding limiting dilational elasticity. With the reorientation model (Fainerman; et al. J. Phys. Chem. 1996, 100, 7669) and the additional assumption of an intrinsic compressibility of the assembled adsorption layer, the data for some oxyethylene surfactants and dodecyl dimethyl phosphine oxide are well described.