(635c) An Instrument for Measuring Dilatational and Shear Rheology of Interfacial Films: Rheosurfr

Complex fluid-fluid interfaces comprise of surface-active materials that reside at air-liquid or liquid-liquid interfaces and display non-trivial rheological responses. They play major roles in a variety of natural and industrial systems, such as biological (lung surfactant, lipid membranes), topical (creams), food (emulsions, foams) and biopharmaceutical (proteins, peptides). Despite their prevalence, obtaining accurate rheological information on such interfacial systems remains challenging to this day.[1] This is partially due to a lack of effective measurement techniques and mathematical frameworks to comprehend them. Common techniques such as the pendant drop and the Langmuir-Pockels trough impart mixed shear and dilatational deformations, and separation of the two poses a significant challenge. To combat this, a radial Langmuir trough was designed that applies pure dilatational deformations and, more recently, a Quadrotrough was designed that can apply either pure dilatational or pure shear deformations.[2] Building on the Quadrotrough design, we have improved the measurement capabilities and can now perform both steady and dynamic measurements, in both shear and dilatational regimes. We demonstrate this new instrument, named RheoSurfR, on a model system of the insoluble glassy polymer poly(tert-butyl methacrylate) (PtBMA). Finally, we will present the complementary characterization techniques that can be performed simultaneously to further our understanding of structure-property relationships of complex fluid-fluid interfaces.

[1] Jaensson, N.; Vermant, J. Current Opinion in Colloid & Interface Science 2018, 37, 136-150. Pepicelli, M.; Verwijlen, T.; Tervoort, T. A.; Vermant, J. Soft Matter 2017, 13 (35), 5977-5990

[2] Tein, Y. S.; Thompson, B. R.; Majkrzak, C.; Maranville, B.; Renggli, D.; Vermant, J.; Wagner, N. J. Review of Scientific Instruments 2022, 93 (9)