Paper Number
SM4 

Session
Polymers Solutions, Melts and Blends

Title
Non-linear rheology of associative polymer gels with tunable interactions

Presentation Date and Time
October 10, 2022 (Monday) 10:50

Track / Room
Track 2 / Sheraton 3

Authors (Click on name to view author profile)

1. Chaub, Arnaud (ESPCI Paris - PSL, Molecular, Macromolecular Chemistry, and Materials)
2. Cloitre, Michel (ESPCI Paris - PSL, Molecular, Macromolecular Chemistry and Materials)

Author and Affiliation Lines (in printed abstract book)
Arnaud Chaub and Michel Cloitre
Molecular, Macromolecular Chemistry, and Materials, ESPCI Paris - PSL, Paris 75005, France

Speaker / Presenter 
Chaub, Arnaud

Keywords
experimental methods; flow-induced instabilities; gels; glasses; polymer solutions; rheometry techniques; suspensions

Text of Abstract
Associative gels are networks made of polymer chains connected by short-lived associations. They can yield and flow when submitted to external mechanical solicitations. These properties make them valuable materials in applications such as 3D printing, injectable gels for tissue reconstruction, or rheology additives for paints and coatings.

Whereas the linear properties of associative gels in the quiescent state or close to equilibrium have been widely studied both experimentally and theoretically, much less is known about their behavior under large deformation. Several fascinating phenomena have been reported - fracture, shear banding, wall slip, self-healing, chaotic motion – but the relation between these deformation mechanisms and the strength of the inter-chains associations is still missing. Here we take on this challenge using a family of associative polymers comprising a polyelectrolyte backbone and lateral pending blocks made of a hydrophilic spacer and a hydrophobic alkyl group. The hydrophobic groups form micelles that connect the polymer chains. The strength of the associations is tuned at will by changing the length of the alkyl groups.

When the alkyl groups comprise 16 carbon atoms or less, the polymers solutions are viscoelastic liquids that flow homogeneously. When the number of carbon atoms increase new properties appear. For 32 carbon atoms, gelation occurs at a well-defined polymer concentration. The non-linear rheology of gels depends on the experimental protocol and the history of applied deformation. To understand this rich and complex behavior, we have performed a multiscale rheo-optical analysis combining macroscopic rheology and in-situ measurements of deformation profiles using a home-made fluorescence microscope. We are able to observe and disentangle multiple flow mechanisms such as wall slip and transient shear banding. These results open the route to a systematic understanding of the flow properties of these associative gels in relation with the strength of the association.