Polyethylene Functionalized with Imidazolium and Pyridinium Moieties through Radiation-Induced Grafting for Alkaline Solid Polymer Electrolyte Membranes

Hydrocarbon-based polymer electrolytes hold great promise for practical electrochemical device deployment but suffer from limitations such as ionic conductivity, alkaline stability, and hydrophobicity. This work reports a new membrane, LLDPE-g-1VIm/4VP, prepared by radiation grafting a binary mixture of 1-vinyl imidazole and 4-vinylpyridine onto linear low-density polyethylene. Short branches in LLDPE are hypothesized to regulate water uptake, thus improving dimensional stability. Under optimized conditions, the membrane exhibits a relatively high ionic conductivity of 39.86 mS cm⁻¹ at 70 °C, good mechanical strength, improved dimensional stability, and moderate alkaline stability even after 240 h at 60 °C under harsh conditions. Preliminary evaluations demonstrate their potential as solid polymer electrolytes for electrochemical energy applications, including alkaline anion exchange membrane fuel cells.