Ion Conductivity of Polyelectrolyte Copolymer Hydrogels with Varying Charge Fraction

Polyelectrolyte (PE) hydrogels enable controlled ion transport critical for next-generation biomedical devices, soft robotics, and water purification technologies. Biological systems often feature polymers with varying charge distribution, influencing their ion transport properties and interactions with surrounding tissues. In this work, we study the ion conductivity of copolymer PE hydrogels formed by random copolymerization of charged and charge neutral comonomers.By varying the fraction of charged monomers and the crosslinking density in a controlled manner, we decouple the effect of the fraction of charged monomers and the pore size on charge concentration and study the effect of the pore size, charge concentration and fraction of charged monomers on ion mobility and ion conductivity of the PE gels. We show that as the fraction of charged monomers increases, the relationship between ion mobility and charge concentration shifts as the polymer chains adopt a more stretched conformation. We examine both anionic copolymer hydrogels and cationic copolymer hydrogels as symmetric model systems, and the experimental results agree with those from molecular dynamics simulations. Our work paves the way for the design of hydrogels mimicking the structural complexity and functional diversity of biological networks.