title: Poly(phenylene) and m-Terphenyl as Powerful Protecting Groups for the Preparation of Stable Organic Hydroxides.
abstract: Four benzimidazolium hydroxide compounds, in which the C2-position is attached to a phenyl group possessing hydrogen, bromine, methyl groups, or phenyl groups at the ortho positions, are prepared and investigated for stability in a quantitative alkaline stability test. The differences between the stability of the various protecting groups in caustic solutions are rationalized on the basis of their crystal structures and DFT calculations. The highest stability was observed for the m-terphenyl-protected benzimidazolium, showing a half-life in 3 M NaOD/CD3OD/D2O at 80 °C of 3240 h. A high-molecular-weight polymer analogue of this model compound is prepared that exhibits excellent mechanical properties, high ionic conductivity and ion-exchange capacity, as well as remarkable hydroxide stability in alkaline solutions: only 5% degradation after 168 h in 2 M KOH at 80 °C. This is the most stable hydroxide-conducting benzimidazolium polymer to date.
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Wright
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Weissbach
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Dr., Burnaby, BC, V5A 1S6, Canada. holdcrof@sfu.ca.
authors.forename: Steven
authors.initials: S
authors.lastname: Holdcroft
keywords: alkaline stability; anion exchange membranes; benzimidazolium; fuel cells; nitrogen heterocycles