Synthesis and Characterization of 4‐Vinylimidazolium/Styrene‐Cografted Anion‐Conducting Electrolyte Membranes

<jats:title>Abstract</jats:title><jats:p>The <jats:italic>β</jats:italic>‐hydrogen‐free imidazole monomer, 2‐methyl‐<jats:italic>N</jats:italic>‐methyl‐4(5)‐vinylimidazole (2M4VIm), is synthesized to prepare anion exchange membranes (AEMs). The radiation‐induced graft polymerization of 2M4VIm and styrene is performed in poly(ethylene‐<jats:italic>co</jats:italic>‐tetrafluoroethylene), followed by <jats:italic>N</jats:italic>‐alkylation and ion exchange reactions to prepare 4‐vinylimidazolium‐containing AEM (2M4VIm/St‐AEM). AEMs that have a 6/4 2M4VIm/St molar ratio and 1.7 mmol g<jats:sup>−1</jats:sup> ion exchange capacity (IEC) result in 75 mS cm<jats:sup>−1</jats:sup> conductivity and 60% water uptake at room temperature in water, demonstrating enhanced values compared to previously reported 2‐methyl‐<jats:italic>N</jats:italic>‐vinylimidazolium‐containing AEMs (2MNVIm/St‐AEM) that have a similar comonomer ratio and IEC. The small‐angle neutron scattering measurements of dry and swollen 2M4VIm/St‐AEM reveal hydrophilic/hydrophobic two‐phase separation, as observed for 2MNVIm/St‐AEM with a similar Im/St composition. 2M4VIm/St‐AEMs exhibit higher alkaline stability in 1 <jats:sc>m</jats:sc> KOH at 80 °C at an early stage owing to the suppression of imidazolium <jats:italic>β</jats:italic>‐elimination but lower long‐term stability than that of 2MNVIm/St‐AEM due to the ring‐opening reaction of the imidazolium group due to its outward orientation from the graft main chain.</jats:p>