Transient modeling of the reversible response of the hydrogel to the change in the ionic strength of solutions

In this paper, a multi-effect-coupling ionic-strength-stimulus (MECis) model, which couples the mechanical, chemical and electrical effects on the swelling/shrinking of the smart hydrogel responsive to the ionic strength of the environmental solution, is presented for the transient analysis of the reversible kinetics of the ionic-strength-sensitive hydrogel. The MECis model is based on the laws of momentum and mass conservation, and considers the poroelasticity of the ionic-strength-sensitive hydrogel. In order to examine the model, the simulation results are compared with the experimental data with reversible swelling-shrinking kinetics, and they are in quite agreement. The reversible characteristics, including the mobile ions concentrations, the fixed charge density, the electric potential and the hydrogel displacement, are studied in order to fully understand the kinetics behavior of the ionic-strength-sensitive hydrogel.