As polymer electrolyte candidates, a series of composite membranes CF3-PSx-PSBOSy-SCNT of copolymer poly[(4-trifluo romethylp henoxy)(4-methylphenoxy)phosphazene]-g-polyf(styrene)(x)-r-[4-(4-sulfobutyloxy)styrene]y} (CF3-PSx-PSBOSy) doped with sulfonated single-walled carbon nanotubes (S-SWCNTs) were prepared. Most of them showed higher proton conductivity than that of Nafion 117. Compared with native membranes, the composite membranes exhibited higher proton conductivity but also a significantly reduced methanol permeability, suggesting a great enhancement effect of S-SWCNTs on the proton conduction and methanol resistance. Specifically, membranes CF3-PS11-PSBOS33-SCNT and CF3-PSBOS45-SCNT showed proton conductivity at 0.46 S/cm and 0.55 S/cm under fully hydrated conditions at 100 degrees C, respectively, which were 2.2-2.6 times as much as that of Nafion 117. Excellent selectivity much more than that of Nafion 117 were also obtained for the composite membranes. (C) 2016 Elsevier B.V. All rights reserved.