Hybrid anion exchange membranes with adjustable ion transport channels designed by compounding SEBS and homo‐polystyrene

Abstract

Hybrid anion exchange membranes (AEMs) were prepared via chemically functionalizing and crosslinking poly(styrene‐b‐[ethylene‐co‐butylene]‐b‐styrene) (SEBS) copolymers and low molecular weight homo‐polystyrene (hPS). Via sequential chloromethylation, crosslinking, quaternization, and alkalization, a series of hPS/SEBS AEMs were obtained with varying content of hPS. Systematic structural, morphological, mechanical, absorption, and transport measurements reveal that these properties depend on the total PS content in the membranes. Particularly, increasing total PS content causes (a) PS domains in the AEMs transition the cylindrical morphology to lamella‐like morphology with comparable correlation length; (b) Young's modulus, water uptake, swelling ratio, ionic exchange capacity and ionic conductivity of the AEMs, and Tg of PS phase increase. In addition, the alkaline stability of the hPS/SEBS AEMs is also improved by addition of hPS. These findings suggest that the proposed method can develop high performance SEBS AEMs that are suitable for fuel cell applications.

SEBS-Based Anion Exchange Membrane Grafted with N-Spirocyclic Quaternary Ammonium Cations for Fuel Cells

“…Alkali stability is an important factor affecting the long-term durability of AEMs. Bae et al reported that polymers without electron-withdrawing groups in the cyclic unit have good alkali stability. , Poly­(styrene- b -(ethylene- co -butylene)- b -styrene) (SEBS) is one of the best choices for the backbone of AEMs on account of the absence of alkali-sensitive aryl ether bonds. − The cation is a critical factor affecting the alkali stability of anion exchange membranes, and their degradation will directly affect the OH – conductivity of the AEMs. Traditional aliphatic quaternary ammonium (QA) cations and aromatic cations are not stable under alkaline conditions on account of S N 2 nucleophilic substitution and Hofmann elimination .…”

Polyolefin‐Based Anion Exchange Membranes with Superior Performance and Long‐Term Durability for Green Hydrogen Production

“…[22][23][24] In particular, in the case of poly(styrene-b-(ethylene-co-butylene)b-styrene) triblock copolymers, the aromatic portion is usually functionalized by chloromethylation or acylation reactions, in the presence of a metal-based catalyst. [25][26][27][28][29] On the other hand, when starting from an unsaturated copolymer, like poly(styreneb-butadiene-b-styrene) (SBS) linear triblock copolymer, it is possible to take advantage of the reactivity of the double bonds of the polybutadiene block to graft a suitable functionalized monomer to the polymer backbone by the use of milder conditions and without ionizing radiations. [30][31][32] By taking advantage of this type of reactivity, AEM copolymer precursors were previously reported to be prepared by in-bulk post-functionalization of SBS with VBC through radical grafting.…”

“…a) Through-plane conductivity at 25 °C. A 1 m KHCO 3 solution was feeded for all the duration of the test; b) Literature data reported in ref [29]…”

Dual-Cation Interpenetrating Polymer Network Anion Exchange Membrane for Fuel Cells and Water Electrolyzers

“…However, low ionic conductivity and poor stability, especially poor chemical stability, have always been the major problems that lie in the way of AEM development. To address the above problems, several strategies have been proposed, including the design of stable cation exchange groups, − alkaline-resistant polymer backbone (e.g., without the benzyl- ether group), − microphase separation, − semi-interpenetrating polymer network (IPN)/IPN structure, cross-linking, − blending, − and hybridization. − Encouraging results have been achieved, for instance, a cross-linked poly­(norbornene) PTFE-supported membrane showed a high conductivity of 198 mS cm –1 @80 °C, with no significant decay after 1000 h under 1 mol L –1 KOH at 80 °C . The poly­(aryl piperidinium) membrane was prepared by inducing the strong basic piperidinium cationic group onto the rigid hydrophobic aryl backbone without the ether bond, which showed conductivity of 170 mS cm –1 @80 °C and durability of over 2000 h …”