Paper Number
PO81 My Program
Session
Poster Session
Title
4D Rheo-SANS investigation of the structure-property relationships of nanoparticle gels
Presentation Date and Time
October 22, 2025 (Wednesday) 6:30
Track / Room
Poster Session / Sweeney Ballroom E+F
Authors
- Egnaczyk, Ted (University of Delaware, Department of Chemical and Biomolecular Engineering)
- Wagner, Norman (University of Delaware)
Author and Affiliation Lines
Ted Egnaczyk and Norman Wagner
Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716
Speaker / Presenter
Egnaczyk, Ted
Keywords
experimental methods; colloids; gels; methods
Text of Abstract
Designing soft materials for specific functionalities under flow conditions is critical for many industrial and scientific communities. Effective measurement of the shear deformation of a soft material’s structure using scattering techniques paired with accurate mechanical measurements can improve the understanding of fundamental material structure-property relationships. In this work, a 4D Rheo-SANS sample environment measures the paired structure and rheological properties of a model thermoreversible gel following a series of thermal and shear conditions. The 4D Rheo-SANS device enables the measurement of the simultaneous rheology and microstructure in all three planes of flow (flow-vorticity, flow-velocity gradient, and velocity gradient-vorticity planes) in addition to kinetic effects measured as a function of time. A model system of adhesive hard spheres comprised of octadecyl-coated silica particles undergoes gelation upon cooling from 40 °C to under 21 °C. The dispersion is rapidly quenched from the sol state to below the gel temperature and the time evolution of the dynamic moduli (G’ and G”) are measured. The resulting shear rheology displays a complex path dependence on the quench rate, quench depth, and application of shear. The competition between gel formation, phase separation, and flow influences the rheology-structure behavior of this model colloidal gel, which we characterize using a sticky hard sphere model to determine a measure of attraction in the system. Results from this study help to unify disparate findings in the field between model depletion gels, which gel as arrested phase separation, and thermoreversible gels with rigidity percolation.