Temperature-stable anion-exchange materials from cyclopolymerization of quaternary ammonium halides

Stimuli-Responsive Macromolecular Architecture by Butler Cyclopolymerizations: Synthesis and Applications

This article reviews the synthesis of polyzwitterions (PZs) (poly-carboxybetaines, -phosphonobetaines, and -sulfobetaines) having multiple pH-responsive centers. The synthesis follows the Butler cyclopolymerization protocol involving a multitude of diallylammonium salts and their copolymerization with SO₂ and maleic acid. The PZs have been transformed into cationic-, anionic-polyelectrolytes, and polyampholytes under the influence of pH. Particular attention is given to the application of these polymers as antiscalants, mild steel corrosion inhibitors, components in constructing Aqueous Two-Phase Systems (ATPSs), and membrane modifiers. The ATPSs could be used to separate various biomolecules, including proteins. Many amphiphilic polymers incorporating a few mol % hydrophobic monomers have shown enhanced viscosities and could be suitable for applications in oil fields. The progress of applying Butler cyclopolymerization in reversible addition-fragmentation chain transfer (RAFT) chemistry has been discussed. Future works are expected to focus on RAFT cyclopolymerization to construct block copolymers.

Prospects for Anion-Exchange Membranes in Alkali Metal–Air Batteries

Rechargeable alkali metal–air batteries have enormous potential in energy storage applications due to their high energy densities, low cost, and environmental friendliness. Membrane separators determine the performance and economic viability of these batteries. Usually, porous membrane separators taken from lithium-based batteries are used. Moreover, composite and cation-exchange membranes have been tested. However, crossover of unwanted species (such as zincate ions in zinc–air flow batteries) and/or low hydroxide ions conductivity are major issues to be overcome. On the other hand, state-of-art anion-exchange membranes (AEMs) have been applied to meet the current challenges with regard to rechargeable zinc–air batteries, which have received the most attention among alkali metal–air batteries. The recent advances and remaining challenges of AEMs for these batteries are critically discussed in this review. Correlation between the properties of the AEMs and performance and cyclability of the batteries is discussed. Finally, strategies for overcoming the remaining challenges and future outlooks on the topic are briefly provided. We believe this paper will play a significant role in promoting R&D on developing suitable AEMs with potential applications in alkali metal–air flow batteries.