Novel partially fluorinated sulfonated poly(arylenethioether)s and poly(aryleneether)s prepared from octafluorotoluene and pentafluoropyridine, and their blends with PBI-Celazol

Due to the expectation that partially fluorinated arylene main-chain ionomers should have better chemical and thermal stabilities than the F-free ionomers, because of the much higher stability of C–F bonds, compared to that of C–H bonds, novel partially fluorinated and sulfonated poly(arylenethioether)s and poly(aryleneether)s were successfully synthesized via nucleophilic polycondensation of 2,3,5,6-tetrafluoropyridine-4-sulfonic acid or 2,3,5,6-tetrafluoro(trifluoromethyl)sulfonic acid with 4,4′-thiobisbenzenethiol (TBBT) or 4,4′-dihydroxybiphenol (BP-OH). All these polymers were analyzed in terms of their thermal stability. Both the novel poly(arylenethioether)s and poly(aryleneether)s were characterized by gel permeation chromatography (GPC). The poly(arylenethioether)s and poly(aryleneether)s were blended with PBI-Celazol to yield base-excess blend membranes. The base-excess blend membranes were doped with H3PO4. All membranes were analyzed in terms of their thermal and oxidative stability in 5% H2O2 solutions. Moreover the blend membranes were characterized by gel permeation chromatography (GPC) before and after the oxidation procedure to get insight into the degradation process. The novel poly(arylenethioether) blend showed excellent thermal stabilities, indicated by a quite high onset temperature of splitting-off of the sulfonic acid group (TSO3Honset) of 442 °C.

In this study we synthesized novel partially fluorinated poly(arylenethioether)s and poly(aryleneether)s and blended these polymers with PBI-Celazol® to yield base excess blend membranes. The polymers and blend membranes were characterized in terms of their thermal stability and we found out, that the blend membranes have much better thermal stabilities compared to the pure polymers. Also the chemical stability of the blend membranes were tested by Fenton test. SPE-OFT-PBI-Celazol had a higher chemical stability compared to SPTE–PFP–PBI–Celazol, due to the higher molecular weight of SPE-OFT.Figure optionsDownload as PowerPoint slideHighlights
► We synthesized novel partially fluorinated polymers.
► The polymers were blended with PBI-Celazol to yield base-excess membranes.
► The novel polymers and blend membranes show excellent thermal stabilities.
► The base-excess membranes exhibit higher proton conductivities, than PBI-Celazol.