Preparation and performance study of naphthol substituted polyphosphazene anion exchange membranes

The main chain of the inorganic polymer polyphosphazene exhibits good alkaline stability, but its poor film-forming properties and excessive water uptake have led to its limited application in the field of anion exchange membranes. In this study, naphthol-substituted polyphosphazene anion exchange membranes demonstrate good film-forming properties and conductivity. When the degree of naphthol substitution reaches around 33%, the hydrophobic main chain and hydrophilic side chain can form a well-defined hydrophilic and hydrophobic phase separation structure. Its ionic conductivity can reach 59.1 mS cm−1 at 80 °C, with a swelling ratio of only 23.5%. Observation under atomic force microscopy reveals that this is due to the introduction of naphthol, which enhances the π-π stacking effect between the main chains, forming a more stable hydrophobic region. Furthermore, when exposed to 4 mol L−1 NaOH at 80 °C for 1000 h, the ionic conductivity of NapP2N-4 decreased by only 19%, and the elongation at break did not significantly decrease, reflecting its good alkaline stability.