Constitutive modeling of bond breaking and healing kinetics of physical Polyampholyte (PA) gel

Abstract

A three-dimensional finite strain nonlinear viscoelastic model is developed to study the mechanical behavior of a physically cross-linked Polyampholyte (PA) gel. The time dependent behavior of this gel is due to the ionic interactions of oppositely charged monomers randomly distributed along the chain backbone. In this work, we divide the physical cross-links broadly into weak and strong bonds, depending on their survival and reformation characteristics. Our constitutive model connects the strain dependent bond breaking and reforming kinetics in the microscopic regime to the deformation of the gel at the continuum level. We compare the predictions of our model with uniaxial tension, tensile-relaxation, cyclic, and small strain torsional relaxation tests. The material parameters in our model are obtained using least squares optimization. Our theory agrees well with the experimental behavior of the gel.