Hydroxide Ion Conducting Membranes Dually Functionalized with Cationic and Zwitterionic Groups

A series of ether-free poly(p-terphenyl piperidinium)s carrying both cationic and zwitterionic groups were prepared evaluated as anion-exchange membranes (AEMs). First, a monomer (zwPip) was synthesized by sulfoalkylation N-methyl-4-piperidone (Pip) using 1,4-butane sultone. Pip zwPip then employed in superacid-mediated polyhydroxyalkylations with p-terphenyl to prepare precursor copolymers containing 20, 30, 40 mol % units. Next, the units fully quaternized Menshutkin reaction iodomethane. AEMs cast from these ion-exchange capacities between 1.8 2.2 m equiv g–1 displayed excellent hydroxide ion conductivities, reaching up 171 mS cm–1 at 80 °C. At lower temperatures, 20 °C, water uptake decreased increasing content, most probably because increased ionic cross-linking through piperidinium–sulfonate complexes. 30 40% showed only minor loss (<10%) when stored 1 M aq NaOH solution °C over period 720 h. The overall results show that co-introduction is an efficient strategy initiate improve performance hydroxide-conducting AEMs.