The influence of RAFT agent on the properties of anion exchange membrane with well-controlled graft structure for fuel cell applications

Abstract

Reversible addition–fragmentation chain transfer (RAFT) agents can be employed to control radical polymerization processes in the synthesis of anion-exchange membranes (AEMs) via radiation-induced grafting (RIG). However, the influence of the RAFT agent content on the performance of anion-exchange membrane fuel cells (AEMFCs) remains largely unexplored. Herein, we present a flexible method for AEM preparation that combines the radiation chemistry of polymers with RAFT polymerization. Low-density polyethylene (LDPE) films were simultaneously irradiated with vinylbenzyl chloride (VBC) monomer and RAFT agent to achieve rigorous control over the molecular weight of the grafted side chains. The incorporation of RAFT agent into the LDPE-grafted polymer chains significantly reduced the degree of grafting, and gel permeation chromatography (GPC) measurements confirmed the reduction in molecular weight. Cross-sectional Raman microscopy revealed that the RAFT protocol also improved graft homogeneity across the polymer matrix. Furthermore, the mechanical properties and surface morphology of the resulting AEMs were enhanced by the use of the RAFT method. The membranes were subsequently characterized in terms of ion-exchange capacity, water uptake, in-plane and through-plane swelling, thermal stability, and hydroxide conductivity. Single-AEMFC tests, as well as chemical stability measurements, demonstrated that RAFT-based AEMs maintained high performance (~1.3 W⋅cm􀀀 2), while exhibiting a markedly lower IEC loss (~30 %) compared to non-RAFT AEMs, thus contributing significantly to AEMFC stability.