Self-Assembly of Surfactants in Nanopores: A Thermodynamic Study of Confinement and Curvature Effects

• Applicant: Professor Dr. Gerhard Findenegg (†)
• Subject Area: Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry
• Term: from 2003 to 2010
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 5410193

This project aims at investigating the effects of confinement and curvature on the aggregative adsorption of nonionic surfactants in cylindrical nanopores. Whereas much progress has been made in recent years towards an understanding of the self-assembly of surfactants on open flat surfaces, little is known about confinement effects and the significance of curvature effects on the aggregative adsorption in narrow pores. These questions will be investigated by studying the adsorption of alkyl ethoxylate (CnEn.) and alkyl glucoside (CnGx.) surfactants of different alkyl chain length and head group sizes in MCM-41 and SBA-15 type mesoporous silicas, which constitute hexagonally ordered arrays of cylindrical pores of uniform size (3 to 12 nm pore diameter). Flow adsorption microcalorimetry will be used to determine the differential molar enthalpies and entropies of adsorption as a function of the degree of pore filling, thus providing a full thermodynamic characterization of the state of surfactant aggregates in the pores. In addition, chromatographic pulse experiments will yield some information about the adsorption kinetics of the surfactants. Details of the experimental program will be planned jointly with the two partner groups of this collaborative project, where static (Gubbins) and dynamic (Schoen/Klapp) aspects of surfactant aggregation in nanopores will be studied by computer simulations. The results of these simulation studies will provide a basis for an interpretation of the experimental results of this project.

• DFG Programme: Research Grants
• International Connection: USA
• Participating Person: Professor Dr. Keith E. Gubbins