International audiencePartially fluorinated poly(arylene ether sulfone) multiblock copolymers bearing perfluorosulfonic functions (ps-PES-FPES), with ionic exchange capacity (IEC) ranging between 0.9 and 1.5 meq H+/g, are synthesized by regioselective bromination of partially fluorinated poly(arylene ether sulfone) multiblock copolymers (PES-FPES), followed by Ullman coupling reaction with lithium 1,1,2,2-tetrafluoro-2-(1,1,2,2-tetrafluoro-2-iodoethoxy)ethanesulfonate. The PES-FPES are prepared by aromatic nucleophilic substitution reaction by an original approach, that is, one pot two reactions synthesis. The chemical structures of polymers are analyzed by H-1 and F-19 NMR spectroscopy. The resulted ionomers present two distinct glass transitions and relaxations revealing phase separation between the hydrophilic and the hydrophobic domains. The phase separation is observed at much lower block lengths of ps-PES-FPES as compared with the literature. AFM and SANS observations supported the phase separation, the hydrophilic domains are well dispersed but the connectivity to each other depends on the ps-PES block lengths. The thermomechanical behavior, the water up-take, and the conductivity of the ps-PES-FPES membranes are compared with those of Nafion 117((R)) and randomly functionalized polysulfone (ps-PES). Conductivities close or higher to those of Nafion 117((R)) are obtained

Perfluorosulfonated poly(arylene ether sulfone) multiblock copolymers have been shown to be promising as proton exchange membranes. The commonly used approach for preparation of the membrane is solvent casting; the properties of the resulting membranes are very dependent on the membrane processing conditions. In this paper, we study the effects of block length, selectivity of the solvent, and thermal treatment on the membrane properties such as morphology, water uptake, and ionic conductivity. DiMethylSulfOxide (DMSO), and DiMethylAcetamide (DMAc) were selected as casting solvents based on the Flory-Huggins parameter calculated by inversion gas chromatography (IGC). It was found that the solvent selectivity has a mild impact on the mean size of the ionic domains and the expansion upon swelling, while it dramatically affects the supramolecular ordering of the blocks. The membranes cast from DMSO exhibit more interconnected ionic clusters yielding higher conductivities and water uptake as compared to membranes cast from DMAc. A 10-fold increase in proton conductivity was achieved after thermal annealing of membranes at 150 °C, and the ionomers with longer block lengths show conductivities similar to Nafion at 80 °C and low relative humidity (30%).