Acid-base interactions between N-heterocycles and sulfonic acid groups are known to mitigate their excessive swelling of hydrocarbon-based proton exchange polymers, but at a cost in a reduction in concentration of...
In this work, the first AB-type primary-chain poly-(arylimidazole) (AB-PAI) homopolymers were synthesized by Debus-Radziszewski polycondensation. Control of the number-average molecular mass (M̅ n ) by ab initio stoichiometry of a monofunctional end-cap provides the first corroborating evidence for this polycondensation proceeding by Carothers' Step-Growth mechanism. Quaternization of imidazole units in AB-PAI yields statistical poly(arylimidazolium) (AB-PAIm) ionenes. Steric protection of the electrophilic imidazolium C2 is encoded in the AB-type monomer.Exceptionally harsh alkaline conditions are required to quantify degradation of the sterically protected AB-PAIm derivative (in 40 wt % NaOD at 80 °C, 20% loss of imidazolium units is observed by NMR after 72 h). All the AB-PAI and the AB-PAIm are thermally stable up to 250 °C in air. The sterically encumbered, polycationic poly(2-[2,6-dimethylphenyl]-1,3-dimethyl-5-phenylimidazolium) hydroxide (IEC (OH) = 2.08 mmol g −1 ) is a transparent red glass that can be solvated by polar organic solvents and is insoluble in water and aqueous alkali metal hydroxides.
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