Anion conducting multiblock copolymers with different tethered cations

Abstract

A multiblock copoly(arylene ether) polymer was used to quantitatively compare the ion conducting channels formed by three different, tethered cation head‐groups. The synthesis allowed for the formation of an exact number of tethers on each repeat unit. Three head‐groups, quaternary trimethylammonium (TMA), quinuclidium (ABCO), and tris(2,4,6‐trimethoxyphenyl)phosphonium (TTMPP) cation head‐groups were compared in terms of size of the conducting channels, ionic conductivity of the mobile hydroxide ion, mechanical properties, quantity of productive and unproductive water, and chemical stability of the membrane in base. The interdomain spacing showed that multiblock copolymers with larger cations formed larger ion conduction channels in the membrane. Larger cations resulted lower ion exchange capacity (IEC) even though the polymer backbone and tether arrangements were identical. TMA was the most stable cation after exposure to 1 M NaOH at 60 °C for 20 days. ABCO had a lower number of bound water molecules and a 22% loss in ion conductivity after treatment in 1 M NaOH at 60 °C for 20 days due to the higher hydroxide ion concentration in the ion conductive blocks. Membranes with TMA head‐groups also had the best mechanical properties. Two membrane preparation methods were compared. The presence of the cation head‐groups assists in phase segregation. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1395–1403

Ether-free polyfluorenes tethered with quinuclidinium cations as hydroxide exchange membranes

“…We have previously studied the thermal stability of poly(phenylene oxide) tethered with different alicyclic cations via alkyl spacers and found that the Qui cations were exceptionally stable with T d,95 ¼ 283 C. Presumably, the cage-like and symmetrical structure signicantly contributes to the excellent thermal stability of this cation. 58…”

Recent Advancement on Anion Exchange Membranes for Fuel Cell and Water Electrolysis

“…The types of cation present in the polymer backbone can also influence the overall properties of the AEMFCs. A detailed study of AEMs using quaternary trimethylammonium, quinuclidium, and phosphonium cations in the polymer backbone indicated that the polymers with quaternary trimethylammonium show superior properties in terms of long‐term alkaline stability and mechanical properties [65] …”

Exploring Side-Chain Designs for Enhanced Ion Conductivity of Anion-Exchange Membranes by Mesoscale Simulations

“…It should also be noted that their earlier work on polystyrene- b -poly­(ethylene- co -butylene)- b -polystyrene (SEBS)–TMA with different spacers has shown that the steric effects of a bulky spacer (or extender) would result in a poorly defined AEM morphology, low water uptake, and a decrease in ion conductivity . There are also recent contributions on more complicated AEMs with branched side-chain modifications, including multiblock copolymer with multihead cationic groups. , …”

“…38 There are also recent contributions on more complicated AEMs with branched side-chain modifications, including multiblock copolymer with multihead cationic groups. 39,40 Molecular simulations provide a tool to gain fundamental understandings of AEM such as the membrane morphology and transport properties, and therefore may accelerate experimental investigations. Detailed mechanisms of the transportation for hydroxide ions in comparison to those for protons in water have been discussed by Tuckerman and coworkers.…”