Paper Number
GS27 

Session
Gels and Self-Assembled Systems

Title
The influence of supramolecular bonds on the nonlinear rheology of metallogels

Presentation Date and Time
October 12, 2017 (Thursday) 8:40

Track / Room
Track 4 / Crestone A

Authors (Click on name to view author profile)

1. Hendricks, Jan (KU Leuven, Department of Chemical Engineering)
2. Brassinne, Jérémy (Solvay, Research and Innovation Centre Lyon)
3. Wilson, James D. (Solvay Novecare, Research and Innovation Centre Paris)
4. Vlassopoulos, Dimitris (FORTH-IESL)
5. Clasen, Christian (KU Leuven)

Author and Affiliation Lines (in printed abstract book)
Jan Hendricks¹, Jérémy Brassinne², James D. Wilson³, Dimitris Vlassopoulos⁴, and Christian Clasen^1
1Department of Chemical Engineering, KU Leuven, Leuven, Belgium; ²Research and Innovation Centre Lyon, Solvay, Saint-Fons, France; ³Research and Innovation Centre Paris, Solvay Novecare, Aubervilliers Cedex, France; ⁴FORTH-IESL, HERAKLION, Greece

Speaker / Presenter 
Hendricks, Jan

Text of Abstract
The behavior of associative polymers under shear receives currently a lot of attention. Depending on the utilized association mechanism and the physical as well as chemical properties of the polymers, a range of complex material responses has been observed when the polymers are exposed to shear flow. In the current study we investigate hydrogels comprised of a polymeric backbone with ligands distributed along the chain. The addition of specific metal ions leads to supramolecular assemblies that form hydrogels if dissolved in water. The hydrogels properties are highly tunable by altering the ratio of metal ions to ligands, the polymer concentration, the density of ligands along the backbone or the metal ion species. An open question is the mechanistic origin of the observed shear thickening as well as shear thinning. This behavior is believed to be related to a flow dependent network volume that could lead to an alteration of the amount of intermolecular bonds and thus a strong rate dependency. To explain the mechanisms leading to these nonlinear shear induced effects, orthogonal superposition measurements were performed by superimposing small amplitude oscillatory shear parallel and orthogonal to a steady shear flow. Using frequency as well as time dependent data collected in both directions we demonstrate how the anisotropy of the hydrogel network structure and morphology is affected by the flow behavior, in order to elucidate the observed macroscopic flow properties. The orthogonal time dependent moduli increase above a certain shear magnitude indicating additional bond formation. The correlated stress relaxation experiments reveal two relaxation modes corresponding to the terminal and the bond breakage and reformation timescales. The later mode is accompanied by temporarily increasing stresses indicating a bond reformation.