Rheology of interfacial layers

Dilational and shear viscoelasticities are important properties of interfacial layers. These quantities are particularly relevant in all systems which contain a huge internal interfacial area such as foams and emulsions. Therefore, also the 3D rheological behavior of foams or emulsions studied by respective methods is superimposed by the 2D interfacial rheology. We report on recent developments in dilational and shear rheology from an experimental point of view as well as discuss the state of the art of the underlying theories. Examples of most relevant experiments are also presented and discussed. Although not yet extensively investigated, the links between bulk rheology of foams and emulsions and the rheology of the corresponding interfacial layers are discussed. Typical frequency dependence of viscoelastic properties. [Display omitted] •Dynamic interfacial properties of surfactants and polymers are essential for understanding foaming and emulsification.•Interfacial rheology helps understand the interaction between adsorbed molecules.•Interfacial rheology is sensitive to changes in molecular conformations or aggregations.•There is recent progress in dilational and shear rheology of liquid interfaces.