Experiments and numerical modeling of the visco-hyperelastic behaviors of polyelectrolyte elastomers

Solvent-free polyelectrolyte elastomers, which are resistant to leakage, hold significant promise for large-scale engineering applications of stretchable ionotronic devices. However, the viscoelastic nature of ionized polymer networks introduces complexities in mechanical performance, highlighting the need for a deeper understanding of their visco-hyperelastic properties. In this study, a poly[1-[2-acryloyloxyethyl]-3-butylimidazolium bis(trifluoromethane) sulfonimide-co-methyl acrylate] elastomer is synthesized as the model material, with controlled covalent crosslinker densities and tailored ionic-to-neutral segment ratios to systematically modify its molecular structures. Through experimental mechanical characterizations—including tensile, hysteresis, and relaxation tests—the effects of network structure and strain rates on the material's responses are investigated. The results reveal a significant rate dependence and the Mullins effect. To model these behaviors, the Yeoh hyperelastic model, incorporating the Mullins effect, is employed to describe the nonlinear elastic response, while a nonlinear power law model is introduced to capture the time-dependent viscoelastic deformation. The proposed modeling framework demonstrates excellent agreements with the experimental data, effectively capturing the complex mechanical behaviors in various tests. This study provides valuable insights into the visco-hyperelastic behaviors of polyelectrolyte elastomers by mapping microscopic molecular structures to macroscopic mechanical performance.