Hydrogen Bonding Dominated Anion-Exchange Membranes Based on Flexible and Rigid Backbones

• Published in: ACS applied polymer materials Vol. 6; no. 19; pp. 12037 - 12048
• Main Authors: Lu, Yuyang, Fan, Huimin, Deng, Cuiwen, Wang, Minhao, Wang, Jia, Feng, Zhongshan, Liu, Yi, Zhou, Xiaorong, Lin, Bencai, Han, Juanjuan
• Format: Journal Article
• Language: English
• Published: American Chemical Society 11.10.2024
• Subjects: fuel cell; poly(4-vinylbenzyl chloride); ethylene vinyl alcohol copolymer; anion-exchange membrane; hydrogen bond cross-linking
• ISSN: 2637-6105; 2637-6105
• DOI: 10.1021/acsapm.4c02188

This work presents a synthesis strategy to yield DQPVB-EVOH anion-exchange membranes (AEMs) by grafting hydroxyl-containing bis-cationic side chains onto a rigid poly­(4-vinylbenzyl chloride) (PVB) backbone (DQPVB) and blending it with a flexible ethylene vinyl alcohol copolymer (EVOH). The intermolecular hydrogen bonding between the hydroxyl groups on DQPVB side chains and those on flexible EVOH delivers good tensile strength (TS = 8.3–22.9 MPa), high elongation at break (EB = 94.9–218.5%), restricted swelling degree (SD = 12.0–42.7%), and high water uptake (WU = 106.8–311.2%) of the AEMs. The bis-cationic properties promote a high ion-exchange capacity (IEC = 2.77–4.01 mmol g–1) for DQPVB-EVOH AEMs, contributing to their improved ionic conductivity (IC = 51.3–89.3 mS cm–1 at 80 °C). Additionally, the absence of polar groups on the PVB backbone, coupled with high water uptake, diminishes the nucleophilic attack ability of hydroxyl groups, resulting in good alkali stability for DQPVB-EVOH AEMs. (After soaking in 1 M KOH at 80 °C for 360 h, IEC retentions = 86.2–93.5% and IC retentions = 85.5–95.6%.) A H2/O2 fuel cell based on the DQPVB-EVOH-0.5 AEM exhibits a maximum power density of 303.6 mW cm–2. In comparison, QPVB-EVOH-0.5, which is formulated by blending singly cationic-grafted quaternized PVB (QPVB) with EVOH, exhibits excessive swelling at 30 °C due to the lack of hydrogen bond cross-linking. It has a SD of up to 95.8% with an IEC of 2.36 mmol g–1, making it not feasible.