Direct Insertion Polymerization of Ionic Monomers: Rapid Production of Anion Exchange Membranes

Abstract

The limited number of methods to directly polymerize ionic monomers currently hinders rapid diversification and production of ionic polymeric materials, namely anion exchange membranes (AEMs) which are essential components in emerging alkaline fuel cell and electrolyzer technologies. Herein, we report a direct coordination‐insertion polymerization of cationic monomers, providing the first direct synthesis of aliphatic polymers with high ion incorporations and allowing facile access to a broad range of materials. We demonstrate the utility of this method by rapidly generating a library of solution processable ionic polymers for use as AEMs. We investigate these materials to study the influence of cation identity on hydroxide conductivity and stability. We found that AEMs with piperidinium cations exhibited the highest performance, with high alkaline stability, hydroxide conductivity of 87 mS cm−1 at 80 °C, and a peak power density of 730 mW cm−2 when integrated into a fuel cell device.

Developing Alkaline Exchange Membranes Using Multisegmented Block Copolymers from Friedel–Crafts Hydroxyalkylation Polycondensation

“…Polyolefin-based AEMs, such as polyethylene, − polypropylene, and polynorbornene, offer advantages such as cost-effectiveness, mechanical stability, and alkaline stability. However, the relatively high swelling ratio in water and poor solution processability makes the polyolefin-based AEMs less attractive than the polyaromatic AEMs. , As such, aryl ether polymers, especially commercialized aryl ether polymers, , are frequently used as the polymer backbone of AEMs.…”

Comparing Ammonium and Tetraaminophosphonium Anion-Exchange Membranes Derived from Vinyl-Addition Polynorbornene Copolymers

“…Ion-exchange membranes are critical components in electrochemical devices, and over the past several years, there has been increased interest in developing hydroxide conducting anion exchange membranes (AEMs) for use in fuel cells (AEMFCs) and water electrolyzers (AEMWEs). − Vinyl addition polynorbornenes (PNBs) have been considered for this purpose, due to the alkaline stable hydrocarbon backbone and tunable properties that can be achieved through polymerization of functional norbornene monomers. − Trimethylammonium-based PNB copolymers have already been explored as membranes in AEMFCs and good performance has been demonstrated, with peak power densities >1 W/cm 2 . , In addition, PNB copolymers have been explored as ionomers in both AEMFCs and AEMWEs. − Given the promise of these materials, furthering our understanding of cationic PNB copolymers will be key to expanding on their use as AEMs (Figure ). ,− …”

“…Some previously reported hydroxide-conducting polymers derived from vinyl addition polynorbornenes. ,− …”

“…The phase separation and tapered character of the tetraaminophosphonium copolymer is beneficial for hydroxide conductivity when compared to other related materials, ,− as this copolymer has the highest conductivity of any tetraaminophosphonium AEM reported to date. Since the trimethylammonium and tetraaminophosphonium PNB copolymers both have excellent stability in 1 M KOH at 80 °C, , fuel cell studies were carried out using both copolymers as membranes. Higher power density was noted for the ammonium copolymer compared to the phosphonium copolymer (1.59 W/cm 2 vs 0.79 W/cm 2 ) as well as enhanced water permeability.…”

Meta-kinks are key to binder performance of poly(arylene piperidinium) ionomers for alkaline membrane water electrolysis using non-noble metal catalysts

“…Progress in AEM materials is impressive, 16–18 yet studies that explicitly address the role of the binder and its optimization are much less prevalent. 15,19,20 Different binder ionomers based on polyethylene, 21,22 polystyrene, 19,23 polysulfones, 24–27 polyphenylene oxides, 28,29 polybenzimidazoles 30,31 or poly(arylene alkylene)s 15,20,32 have been used. Beside these, also Nafion 33,34 and polytetrafluoroethylene 34–36 have been reported.…”