Sulfonated poly(ether ether ketone) membranes crosslinked with sulfonic acid containing benzoxazine monomer as proton exchange membranes

The incorporation of benzoxazine (Ba) or sulfonic acid containing benzoxazine (SBa) as a crosslinking agent in SPEEK proton exchange membrane (PEM) can substantially improve the SPEEK membrane performance. The SPEEK-SBa membranes give higher effective selectivity than corresponding SPEEK-Ba membranes under close crosslinker loading and thus are more suitable to be used in direct methanol fuel cells. The best achieved SPEEK-SBa composition (SBa40) gives reasonable proton conductivity (0.91 x 10(-2) S cm(-1)) but significantly lower methanol permeability (6.5 x 10(-8) 52 cm(-1)). The achieved effective selectivity (Phi = SPEEK-SBa40: 14.0 x 10(4) S s cm(-3)) is substantially higher than the plain SPEEK (Phi = 7.24 x 10(4) S s cm(-3)) which has great potential for practical applications in DMFCs. (C) 2009 Elsevier Ltd. All rights reserved.