Preparation and Characterization of Tetra-Imidazolium Hydroxide Polyphenylene Membranes via Nickel Catalyzed C–C Coupling Polymerization

Abstract

Imidazolium hydroxide anion exchange membranes functionalized with conjugated tetraphenylethylene moieties were synthesized via Ni(0) catalyzed polymerization by sequential chloromethylation, substitution with imidazoliums and ion exchange. Moreover, with their pendant benzoyl groups the copolymers showed high molecular weight, durability, thermo-oxidative stability, high solubility in polar aprotic solvents and strong chemical and thermal stability in comparison to alkyl quaternary ammonium-functionalized polymers. The proposed polymer membranes, without ether linkages, demonstrated improved performance in ion exchange capacity, water uptake, ion conductivity, and thermal stability. The polymer membranes were studied by 1 H-NMR (Nuclear Magnetic Resonance) spectroscopy, thermogravimetric analysis, water uptake, ion exchange capacity and ion conductivity. Surface morphologies were assessed by atomic force microscope (AFM). The synthesized polymers may have applications as fuel cell membranes because of their excellent ion conductivity.