Deformation, Creep, and Dynamics in Glassy Ionomers

The mechanical response of ion‐containing polymer glasses reflects a competition between covalent connectivity and reversible electrostatic associations, yet how ionic motifs govern yielding, strain hardening, and creep remains unclear. Here we use nonequilibrium molecular dynamics to compare two model ionomer architectures: a polyampholyte in which oppositely charged groups are tethered to the same chains, and a cationic ionomer in which counterions remain mobile, against a neutral control. All three systems share essentially the same small‐strain elastic modulus, showing that van der Waals interactions set the elastic baseline. In contrast, ionic associations strongly reinforce the post yield regime: both ionomers exhibit larger yield stresses and higher strain‐hardening moduli, with the polyampholyte showing the strongest reinforcement. Under creep, the neutral control fluidizes at high stress, the cationic ionomer shows delayed fluidization, and the polyampholyte remains predominantly solid‐like within the simulated window. Microscopic analysis shows that ionic aggregates suppress transverse mobility and sustain stress heterogeneity. These results identify ionic architecture as a practical design variable for decoupling small strain stiffness from post yield toughness and long‐time creep resistance in ionomer glasses.