Paper Number
IR15                         My Program 

Session
Interfacial Rheology, Surfactants, Foams and Emulsions

Title
Effects of molecular architecture at liquid interfaces: Interfacial rheology and neutron reflectometry of linear, ring, and dendritic polymers

Presentation Date and Time
October 20, 2025 (Monday) 4:45

Track / Room
Track 5 / O’Keeffe + Milagro

Authors (Click on name to view author profile)

  1. Renggli, Damian (University of Delaware, Chemical and Biomolecular Engineering)
  2. Thompson, Benjamin (University of Delaware, Chemical and Biomolecular Engineering)
  3. Allgaier, Jürgen (Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science)
  4. Krutev, Margarita (Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science)
  5. Richter, Dieter (Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science)
  6. Lin, Ting-Chih (Carnegie Mellon University, Department of Chemistry)
  7. Matyjaszewski, Krzysztof (Carnegie Mellon University, Department of Chemistry)
  8. Vlassopoulos, Dimitris (FORTH and University of Crete, Institute of Electronic Structure and Laser)
  9. Wagner, Norman (University of Delaware)

Author and Affiliation Lines (in printed abstract book)
Damian Renggli1, Benjamin Thompson1, Jürgen Allgaier2, Margarita Krutev2, Dieter Richter2, Ting-Chih Lin3, Krzysztof Matyjaszewski3, Dimitris Vlassopoulos4 and Norman Wagner1
1Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716; 2Jülich Centre for Neutron Science, Forschungszentrum Jülich GmbH, Jülich 52425, Germany; 3Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA 15213; 4Institute of Electronic Structure and Laser, FORTH and University of Crete, Heraklion 71110, Greece

Speaker / Presenter 
Renggli, Damian

Keywords
experimental methods; interfacial rheology; rheometry

Text of Abstract
Liquid—air interfaces provide confinement for insoluble polymeric networks to two-dimensional mono-molecular configuration where entanglements akin to three-dimensional (bulk) networks are not possible. In the absence of free ends, ring-shaped polymers accommodate topological constraints of their neighbors by adapting a loopy conformation that is described by the fractal loopy globule model. The loops are local double-folded segments. Dendrimers have the ability to interdigitate their dangling ends in two dimensions, and are known for their hierarchy of modes, where relaxation starts at the outermost dangling ends and moves sequentially to lower branching generations. These ‘entangled’ configurations will strongly influence the properties of said interfaces compared to linear polymers. A novel multimode interfacial rheometer (RheoSurfR www.stf-technologies.com) enables measurement of the isotherm as well as dilatational and shear interfacial rheology (both steady and dynamic), as well as in situ microstructural characterization by neutron reflectometry and Brewster angle microscopy. The latter enable determination of the surface excess and interfacial molecular structure, respectively. Contrast for neutron reflectometry is achieved by selective deuteration of the polymer and contrast variation of the water phase. We carefully investigate linear and ring conformations of poly(ethylene oxide) (PEO) and poly(methyl acrylate) (PMA) at varying compressions (i.e., confinement) and compare them to linear and Caley-Tree-like dendritic poly(methyl methacrylate) (PMMA). We observe strong changes in interfacial structure and hence compression isotherms (i.e., thermodynamic properties), while effects on interfacial rheology are more subtle, with dendritic PMMA having the strongest effect. The results of microstructural characterization are useful for interpreting these results. This work elucidates the effects of molecular architecture on interfacial entanglements; a concept not understood yet.