Highly durable polymer electrolyte membranes at elevated temperature: Cross-linked copolymer structure consisting of poly(benzoxazine) and poly(benzimidazole)

► Cross-linked copolymers were prepared by PBI and difunctional benzoxazine. ► Excellent thermal and mechanical stabilities of cross-linked copolymer membranes. ► Performance and durability of cross-linked copolymer membranes was highly enhanced.