▪ Abstract The past 10 years have witnessed a tremendous acceleration in research devoted to non-fluorinated polymer membranes, both as competitive alternatives to commercial perfluorosulfonic acid membranes operating in the same temperature range and with the objective of extending the range of operation of polymer fuel cells toward those more generally occupied by phosphoric acid fuel cells. Important requirements are adequate membrane mechanical strength at levels of functionalization (generally sulfonation) and hydration allowing high proton conductivity, and stability in the aggressive environment of a working fuel cell, in particular thermohydrolytic and chemical stability. This review provides an overview of progress made in the development of proton-conducting hydrocarbon and heterocyclic-based polymers for proton exchange and direct methanol fuel cells and describes the various approaches made to polymer modification/synthesis and salient properties of the materials formed, including those relati...

Non-Fluorinated Polymer Materials for Proton Exchange Membrane Fuel Cells

Sulfonated hydrocarbon membranes for medium-temperature and low-humidity proton exchange membrane fuel cells (PEMFCs)

Sulfonated and crosslinked polyphosphazene-based proton-exchange membranes

Photo-irradiation for preparation, modification and stimulation of polymeric membranes

Thermally stable polymers for advanced high-performance gas separation membranes

: Dense films of poly((4-ethylphenoxy)(phenoxy)phosphazene), PEPP, a potentially attractive ion-exchange membrane material, were crosslinked to varying degrees using UV light and a photoinitiator. This polymer contained two kinds of substituents: phenoxy groups to be used for possible functionalization (e.g. , sulfonation) and ethylphenoxy sidechains for photocrosslinking, where hydrogens at the benzylic carbons could be abstracted by a photoinitiator leaving macroradicals that after recombination formed covalent bonds. The polyphosphazene polymer was synthesized, mixed with a photoinitiator, shaped into a thin film by solvent casting, and irradiated with UV light for a specified period of time. Benzophenone, BP, was selected as the photoinitiator because it was miscible with polyphosphazene, had the highest rate of hydrogen abstraction and absorbed UV light of 365 nm wavelength. The half-life of benzophenone in 50 micrometers thick irradiated films was determined to be 20 min. When the BP-PEPP molar ratio was increased from 0 to 0.5 the glass transition temperature increased after irradiation from -8.8 to 53.5 deg C. At the same time the equilibrium swelling in dimethylacetamide, at 25 deg C, decreased from infinity to 0.31. Tensile strength tests of the crosslinked films revealed a nonlinear dependence on BP-PEPP molar ratio. jg p2

Sally O'Connor

Papers

Polyphosphazene membranes. I. Solid‐state photocrosslinking of poly[(4‐ethylphenoxy)‐(phenoxy)phosphazene]