Please join the Department of Chemical and Biological Engineering for a seminar titled, “Surfactant Adsorption at the Water/Alkane Interface – Competitive and Cooperative Effects Between Surfactant and Alkane Molecules” on April 6 via Zoom. The seminar will be given by Dr. Rer. Nat. Habil. Reinhard Miller, Senior Scientist in the Department of Soft Matter Biophysics at Technische Universität Darmstadt.
What: Surfactant Adsorption at the Water/Alkane Interface – Competitive and Cooperative Effects Between Surfactant and Alkane Molecules
When: April 6, 2022, 3:15 p.m. – 4:30 p.m.
Where: Online via Zoom, https://iit-edu.zoom.us/j/86144138024?pwd=NzViRzZLb01XQXVibDdrY3NyTkxLUT09
Meeting ID: 861 4413 8024
Passcode: 757162
Biography
Dr. Rer. Nat. Habil. Reinhard Miller
Senior Scientist, Department of Soft Matter Biophysics
Technische Universität Darmstadt
Studied Math in Rostock and Colloid Science in Dresden, Germany. Worked first at the Academy of Sciences in Berlin and from 1991 to 2019 at Max Planck Institute of Colloids and Interface in Potsdam. Since then he works as senior scientist at the Technical University Darmstadt. His main scientific interests are dynamics and thermodynamics of adsorption of surfactants, proteins, polymers, particles and their mixtures at liquid interfaces, dilational and shear surface rheology, formation and stabilization of foams and emulsions. He published his scientific results in about 650 papers in peer-reviewed journals and many books and book chapters. He is editor of the journals Advances in Colloid and Interface Science and Colloids & Interfaces.
Abstract
The theory of surfactant adsorption at water/oil interfaces was based for a long time on models derived for the water/air interface. This was the main reason for the fact, that many experimental observations could not be adequately described. Therefore, a number of observations, peculiar for water/oil interfaces, were mainly explained by the penetration of oil molecules into the interfacial layer.
Recently, a competitive mechanism for the adsorption of surfactant at the water/oil interface was proposed, which provides a much better description of experimental data. This idea assumes that oil molecules compete with the surfactant molecules at the interface. However, this picture does not allow explaining why the interfacial tension of the water/oil interface decreases significantly already at extremely low surfactant concentrations in the aqueous phase. It was found out, that this phenomenon is cause by a cooperativity of surfactant and oil molecules in the interfacial layer. Cooperativity in this sense means that already few surfactant molecules adsorbed at the interface can induce a significant ordering of oil molecules in the interfacial layer. And in turn, this new interfacial structure attracts further surfactant molecules to adsorb.
A refinement for the theoretical description of experimental data was finally achieved by applying suitable adsorption models for the two adsorbing compounds, i.e. a Frumkin adsorption model for the adsorption of oil molecules, and for the adsorption of surfactant molecules, depending on the surfactant’s molecular structure, a Langmuir, Frumkin, or reorientation model is suitable.