title: Sorption and Interfacial Rheology Study of Model Asphaltene Compounds.
abstract: The sorption and rheological properties of an acidic polyaromatic compound (C5PeC11), which can be used to further our understanding of the behavior of asphaltenes, are determined experimentally. The results show that C5PeC11 exhibits the type of pH-dependent surface activity and interfacial shear rheology observed in C6-asphaltenes with a decrease in the interfacial tension concomitant with the elastic modulus when the pH increases. Surface pressure-area (Π-A) isotherms show evidence of aggregation behavior and π-π stacking at both the air/water and oil/water interfaces. Similarly, interactions between adsorbed C5PeC11 compounds are evidenced through desorption experiments at the oil/water interface. Contrary to indigenous asphaltenes, adsorption is reversible, but desorption is slower than for noninteracting species. The reversibility enables us to create layers reproducibly, whereas the presence of interactions between the compounds enables us to mimic the key aspects of interfacial activity in asphaltenes. Shear and dilatational rheology show that C5PeC11 forms a predominantly elastic film both at the liquid/air and the liquid/liquid interfaces. Furthermore, a soft glassy rheology model (SGR) fits the data obtained at the liquid/liquid interface. However, it is shown that the effective noise temperature determined from the SGR model for C5PeC11 is higher than for indigenous asphaltenes measured under similar conditions. Finally, from a colloidal and rheological standpoint, the results highlight the importance of adequately addressing the distinction between the material functions and true elasticity extracted from a shear measurement and the apparent elasticity measured in dilatational-pendant drop setups.
authors.affiliation: Ugelstad Laboratory, Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU) , NO-7491 Trondheim, Norway.
authors.forename: Diego
authors.initials: D
authors.lastname: Pradilla
authors.affiliation: Ugelstad Laboratory, Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU) , NO-7491 Trondheim, Norway.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Simon
authors.affiliation: Ugelstad Laboratory, Department of Chemical Engineering, Norwegian University of Science and Technology (NTNU) , NO-7491 Trondheim, Norway.
authors.forename: Johan
authors.initials: J
authors.lastname: Sjöblom
authors.affiliation: Soft Materials Laboratory, Department of Materials, ETH Zürich , Vladimir-Prelog-Weg 5, 8093 Zürich, Switzerland.
authors.forename: Joseph
authors.initials: J
authors.lastname: Samaniuk
authors.affiliation: Institute of Chemical Technology and Engineering, Poznan University of Technology , Berdychowo 4, 60-965 Poznan, Poland.
authors.forename: Marta
authors.initials: M
authors.lastname: Skrzypiec
authors.affiliation: Soft Materials Laboratory, Department of Materials, ETH Zürich , Vladimir-Prelog-Weg 5, 8093 Zürich, Switzerland.
authors.forename: Jan
authors.initials: J
authors.lastname: Vermant