Synthesis of poly(arylene ether sulfone)s with locally and densely sulfonated pentiptycene pendants as highly conductive polymer electrolyte membranes

Poly(aryl ether sulfone)s containing sulfonated pentiptycene groups SPES-x-PPD are firstly synthesized through nucleophilic aromatic substitution polycondensation by using pentiptycene-6,13-diol, bis(4-hydroxyphenyl) sulfone and 4,4′-difluorodiphenyl sulfone, followed by postsulfonation with concentrated sulfuric acid at room temperature. The structures of SPES-x-PPD are characterized by IR, 1H NMR and 13C NMR spectra. These ionomers generally show high thermal stability. Transmission electron microscopic observations reveal that SPES-x-PPD membranes form well-defined microphase separated structures. SPES-40-PPD with the IEC value 2.36 mmol g−1 shows conductivity of 2.6 × 10−1 S cm−1 which is much higher than that of perfluorinated Nafion 117 membrane (1.1 × 10−1 S cm−1) at 80 °C and 94% RH. At 80 °C and 34% RH, SPES-40-PPD membrane displays the conductivity of 2.7 × 10−3 S cm−1 which is comparable with that of Nafion 117 membrane (3.0 × 10−3 S cm−1).

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The synthesis of poly(aryl ether sulfone)s containing locally and densely sulfonated pentiptycene groups (SPES-x-PPD) is firstly reported. ► The well-defined micro-phase separated structures is observed for SPES-x-PPD membranes. ► These novel SPES-x-PPD membranes achieved high proton conductivity in a range of 34–94% RH.