Paper Number
GG51 

Session
Rheology of Gels, Glasses and Jammed Systems

Title
Low-frequency elastic plateau in linear viscoelasticity of polyelectrolyte coacervates

Presentation Date and Time
October 12, 2022 (Wednesday) 5:25

Track / Room
Track 3 / Sheraton 5

Authors (Click on name to view author profile)

  1. Li, Huiling (University of Michigan-Ann Arbor, Macromolecular Sciecnce and Engineering)
  2. Shetty, Abhishek (Anton Paar USA Inc., Rheology Department, Advanced Technical Center)
  3. Liu, Ying (University of Michigan-Ann Arbor, Macromolecular Sciecnce and Engineering)
  4. Larson, Ronald (University of Michigan-Ann Arbor, Chemical Engineering Department)

Author and Affiliation Lines (in printed abstract book)
Huiling Li1, Abhishek Shetty2, Ying Liu1 and Ronald Larson3
1Macromolecular Sciecnce and Engineering, University of Michigan-Ann Arbor, Ann Arbor, MI 48105; 2Rheology Department, Advanced Technical Center, Anton Paar USA Inc., Ashland, VA 23005; 3Chemical Engineering Department, University of Michigan-Ann Arbor, Ann Arbor, MI 48105

Speaker / Presenter 
Li, Huiling

Keywords
experimental methods; consumer products; gels; polymer solutions

Text of Abstract

The appearance of elastic plateau in the low frequency region of linear viscoelasticity of polyelectrolyte coacervates has been reported repeatedly. However, the reliability and formation of this unusual gel-like behavior are still mysterious. Here we will present a thorough study of the effect of salt concentration and polymer chain lengths on the low-frequency elastic plateau of coacervates by conducting frequency sweeps. The reliability and reproducibility of these measurements are carefully checked by determining the frequency-dependent stress limits of the rheometer through use of reference fluids, and by repeat experiments with coacervates. Long-time frequency sweeps show that coacervates with less salt are more repeatable than those with higher salt. It is observed that a low-frequency plateau only reliably appears below a critical salt concentration, and the magnitude of the plateau depends strongly on salt concentration and on chain lengths of both polycation and polyanion. It is suggested that a possible cause of this gel behavior in the low frequency region is the formation of aggregates of multiple charged monomers, due to formation of “ionomer-like regions” at low salt concentration and lower hydration levels.