A phase-field model for systems with coupled large deformation and mass transport

Phase-field model is a powerful tool for studying the microstructure evolution of materials. This paper seeks to introduce phase-field modeling to the field of soft materials, especially for studying polymeric gels. A general framework for the field theory of coupled large deformation and mass transport is established, and two specific models of diffuse interface are proposed. The ideal liquid-like interface has a deformation-independent energy and gives rise to a constant surface tension, and a non-ideal interface would result in a strain-dependent surface stress. Either model gives a stress field consistent with the effect of interface line force. The field theory is implemented into a finite-element code, and several numerical examples are calculated with representative material models in which deformation is weakly or strongly coupled with mass transport. The numerical models demonstrate the versatility of the phase-field methodology, and reveal some interesting phenomena due to the coupling. For example, the composition of a separated phase is significantly affected by the kinematic constraint, and varies during coarsening.