Polyphosphazenes

Abstract

An overview of polyphosphazene science is given. A brief history of over 100 years of synthetic developments is presented, from the work of Stokes to the latest cationic condensation polymerization, followed by discussions of blending, cross‐linking, and functionalization. Applications of polyphosphazenes as elastomers, solid polymer electrolytes, membranes, and flame retardants are reviewed. Biomedical research is referenced and hybrid polyphosphazenes and polymers containing cyclophosphazenes are also covered briefly. Although the limitless derivatization possibilities along with the attractiveness of the inorganic P–N backbone has generated enormous scientific interest in polyphosphazenes, current synthetic routes are characterized by high costs of the substrates, high instability of the intermediate polydichlorophosphazene, and sensitivity of the resultant polyphosphazene to the synthesis conditions. The need for costly process equipment must also be taken into account when assessing the cost of synthesizing polyphosphazenes on a commercial scale. Initial manufacturing efforts by Firestone, Ethyl Corporation, and Elf Atochem were terminated, but various polyphosphazene derivatives are available from custom synthesis companies. Therefore, polyphosphazenes should be considered still under the development stage.

Power Output and Durability of Electrospun Fuel Cell Fiber Cathodes with PVDF and Nafion/PVDF Binders

“…Fuel cell tests were carried out to compare beginning-of-life (BoL) and end-of-life (EoL) fuel cell power output after a carbon corrosion voltage cycling experiment for nanofiber 17 We have found that well-mixed PVDF/Nafion blends with nanometer-size domains can be prepared by electrospinning Nafion + PVDF mixtures. 18 The present paper does not deal with the chemistry/morphology of Nafion/PVDF blended fibers, (this topic will be addressed in separate publications), but only with the use of these blends as binders in hydrogen/air fuel cell cathodes.…”