Rational Design of Ionomer Microstructures for Thermally Reprocessable Materials with Creep Resistance and Recoverability

Designing dynamic polymer networks that resist creep while remaining reprocessable is a central challenge in sustainable polymeric materials development. Here, we report charge-neutral diblock copolymers (i.e., ionomers) with 18 mol % ammonium chloride that combine high creep resistance and recoverability (>90% recovery after five creep cycles) with thermal processability (compression moldable at 80 °C), outperforming conventional statistical ionomers that soften at elevated temperatures due to ion dissociation. Unlike the 1-3 nm ionic clusters formed in statistical ionomers, these diblock ionomers self-assemble into an inverse hexagonal (iHEX) morphology where glassy ionic domains form the continuous matrix and rubbery neutral domains form the cylinders. The rigid ionic scaffold and large interdomain spacing (>30 nm) substantially extend chain pull-out times and interdomain diffusion, imparting elasticity, while the unentangled flexible blocks within the rubbery cylinders enable processability. By demonstrating that precise control over ion distribution can convert a thermoplastic-like ionomer into a reprocessable elastomer, this work establishes a general design principle for creating nanostructured dynamic polymers with enhanced mechanical integrity, recoverability, and sustainability.