A novel approach to prepare photocrosslinked sulfonated poly(arylene ether sulfone) for proton exchange membrane

• Novel photosensitive sulfonated poly(arylene ether sulfone) (SPAES) was synthesized.
• Crosslinked SPAES membranes were obtained by UV irradiation in a hydrated state.
• Low methanol crossover and high proton conductivity were achieved in crosslinked PEMs.
• Photocrosslinking improved mechanical, oxidative and hydrolytic stabilities of SPAES.

Novel sulfonated poly(arylene ether sulfone)s with photo-crosslinkable chalcone moiety in the main chain (SPAESs) are synthesized from 4,4′-dihydroxychalcone, 3,3′-disulfonate-4,4′-difluorodiphenylsulfone and 4,4′-difluorodiphenylsulfone. The resulting polymers are characterized by FT-IR, 1H NMR, UV and TGA techniques. SPAES membranes are photocrosslinked without using a photoinitiator in a hydrated state by UV irradiation (365 nm) to preserve the percolated hydrophilic channels in the hydrated membranes. Untreated SPAES membranes demonstrate high proton conductivity up to 211.61 mS cm−1 at 80 °C for SPAES50. Photocrosslinked SPAES50 membrane maintains proton conductivity up to 191.06 mS cm−1. The photocrosslinking strategy of SPAES membranes in a hydrated state helps reducing the methanol permeability without sacrificing proton conductivity. Methanol permeability of crosslinked SPAES30 membrane was measured to be in the range from 1.23×10−7 cm2 s−1 to 6.48×10−8 cm2 s−1, which is only 1/36 of that of Nafion® 117. Photocrosslinked SPAES membranes also exhibit excellent mechanical and thermal properties, and improved oxidative and hydrolytic stability.

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