Modeling of effect of initial fixed charge density on smart hydrogel response to ionic strength of environmental solution
Abstract
A chemo-electro-mechanical model is presented for analysis of the influence of the initial fixed charge density on performance of ionic-strength-sensitive hydrogel, termed the multi-effect-coupling ionic-strength-stimulus (MECis) model. It is composed of Nernst–Planck convection–diffusion equations which describe the chemical field, Poisson equation which provides the electrical potential associated with the fixed charge equation based on the Langmiur adsorption theory, and the mechanical equation which demonstrates the deformable behavior of the polymeric network of the ionic-strength-sensitive hydrogel. In the MECis model, the ionic strength of the bathing solution is considered as a key stimulus and incorporated into the Nernst–Planck equations and fixed charge formulation via activity coefficient and apparent dissociation constant, which influence the convection–diffusion characteristics and binding reaction. The initial fixed charge density is taken as an important chemical parameter for the indication of the amount of the ionizable monomer