Sulfo-Phenylated Polyphenylenes Containing Sterically Hindered Pyridines

Abstract

We systematically investigated the effect of incorporating a sterically hindered pyridyl group into a sulfophenylated polyphenylene to control the polymer's physicochemical properties through acid−base interactions. Homopolymers with similar molecular weights and comparable structures that vary by only one atom (N− vs C−) per repeat unit along the polymer chain were prepared. Compared to a non-pyridyl reference membrane, incorporation of a pyridyl group improves the oxidative stability against free radicals, increases the elongation at break to 55% (from 37%), and enhances the thermal stability to 326 °C (from 246 °C). In an accelerated fuel cell degradation test, polymeric membranes containing the sterically encumbered pyridyl unit exhibited exceptional stability (0.16 mV h −1 degradation rate over 1000 h) and retained ∼80% of their peak power density over this time.

Hydrocarbon-based Pemion™ proton exchange membrane fuel cells with state-of-the-art performance

“…Previously reported chemical stability data showed that sulfonated phenylated polyphenylenes can withstand 1000 h OCV stress test at exceptionally low degradation rates of 0.16 mV h À1 , 23 without incorporation of radical scavengers. This excellent stability in combination with the promising performance shown in the present study thereby represents a signicant step in the development of next-generation MEAs for hydrogen fuel cells.…”

“…A common polymer architecture employed in such materials is the polyphenylene backbone, which unlike preceding poly(arylene ether)s and numerous derivatives thereof, contain no backbone linkages particularly susceptible to chemical degradation. 1 For example, Skalski et al, 19 Adamski et al, 20 Miyake et al, 21 Shiino et al, 22 Xu et al, 23 and Shimizu et al, 24 reported PEMs with best-in-class chemical durability, all based on a polyphenylene backbones. Compared to PFSAs, however, the reported ex situ and in situ durabilities of hydrocarbon polyphenylene-based PEMs have been contradictory.…”

“…10 3 times greater for polyphenylene, 25 the in situ lifetime of polyphenylene PEMs is >3Â greater when evaluated in an open circuit voltage (OCV) accelerated stress test (AST) using the DOE protocol. 20,23 In terms of ex situ electrochemical characteristics, numerous polyphenylene-based membranes exhibit measurably greater proton conductivity than PFSAs such as Naon 211 at high humidity. At low humidity, however, proton conductivity declines disproportionately due to a greater dependence on water content on proton conduction.…”

Diels–Alder cycloaddition polymerization of highly aromatic polyimides and their multiblock copolymers

“…Upon adding a 4-fold excess of tetraphenylcyclopentadienone 4 to the imide diyne 3, a full conversion of the terminal alkyne to give compound 5 was observed by 13 C-NMR spectroscopy (see ESI86). The conditions required for this reaction were found to be 260 °C in diphenyl ether for 72 h. Buoyed by this observation, we then prepared a bifunctional diene 6 in Scheme 2 according to literature procedures 18,35 . Compound 6 underwent a Diels-Alder polymerization with diyne 3 to yield the polymer PI-1, a highly aromatic soluble polyimide.…”

On the evolution of sulfonated polyphenylenes as proton exchange membranes for fuel cells

“…Open 31,66,67,69,72,73,212,213 This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.…”