Paper Number
GG22 

Session
Arrested Systems: Gels and Glasses

Title
Local mechanism governing the global reinforcement of filler-hydrogel composites

Presentation Date and Time
October 13, 2021 (Wednesday) 11:05

Track / Room
Track 6 / Ballroom 1

Authors (Click on name to view author profile)

  1. Dellatolas, Ippolyti (Massachusetts Institute of Technology, Mechanical Engineering)
  2. Bantawa, Minaspi (Georgetown University, Department of Physics)
  3. Damerau, Brian (Georgetown University)
  4. Divoux, Thibaut (ENS Lyon, CNRS)
  5. Del Gado, Emanuela (Georgetown University)
  6. Bischofberger, Irmgard (Massachusetts Institute of Technology, Mechanical Engineering)

Author and Affiliation Lines (in printed abstract book)
Ippolyti Dellatolas1, Minaspi Bantawa2, Brian Damerau2, Thibaut Divoux3, Emanuela Del Gado2 and Irmgard Bischofberger1
1Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139; 2Department of Physics, Georgetown University, Washington, DC 20057-0004; 3CNRS, ENS Lyon, Lyon, France

Speaker / Presenter 
Dellatolas, Ippolyti

Keywords
experimental methods; computational methods; applied rheology; composites; gels; glasses

Text of Abstract
The reinforcement of hydrogels by the addition of filler particles usually requires a filler content of ~50%. Here, we probe the linear viscoelastic properties of soft hydrogels containing filler nanoparticles and reveal that significant reinforcement can be achieved at unexpectedly low volume fractions of fillers when the fillers and the polymer are attractive. At ~10% volume fraction of fillers we report a tenfold increase in the modulus of the composite material, independent of polymer concentration, polymer type and filler size. We show that this robust reinforcement can be rationalized with an effective medium theory that holds for attractive filler-gel systems. Using 3D numerical simulations, we probe the microscopic structure and dynamics of the reinforced gels to provide a microscopic origin of the reinforcement. We show that the attractive interaction between the fillers and the gel induces an increase in the local gel density around the fillers, which in turn constrains the gel displacements and couples the stresses throughout the system. These local changes in the gel structure around the fillers lead to a global reinforcement of the filler-gel composite.