Synthetic Strategies toward Arylene-Based Anion Exchange Membranes with High Local Molecular Flexibility
(2026)- Abstract
- Durable and high-performing anion-exchange membranes (AEMs) are key components in alkaline water electrolyzers and fuel cells. As potentially more sustainable and cost-effective alternatives to proton exchange membrane (PEM)-based systems, AEM-based devices can operate without platinum-group metal catalysts or perfluorinated polymers. However, their broader practical implementation remains limited by insufficient alkaline stability and lower hydroxide conductivity. Moreover, because AEMs must balance multiple interrelated properties for operation in different electrochemical devices, versatile synthetic strategies are particularly important for their development.
Introducing molecular flexibility into AEMs has emerged as an effective... (More) - Durable and high-performing anion-exchange membranes (AEMs) are key components in alkaline water electrolyzers and fuel cells. As potentially more sustainable and cost-effective alternatives to proton exchange membrane (PEM)-based systems, AEM-based devices can operate without platinum-group metal catalysts or perfluorinated polymers. However, their broader practical implementation remains limited by insufficient alkaline stability and lower hydroxide conductivity. Moreover, because AEMs must balance multiple interrelated properties for operation in different electrochemical devices, versatile synthetic strategies are particularly important for their development.
Introducing molecular flexibility into AEMs has emerged as an effective strategy to address these limitations. This thesis develops two complementary synthetic platforms for incorporating controlled molecular flexibility into ether-free AEMs: (i) through alkaline-stable flexible spacers in the side chains, with particular attention to 4-position-functionalized piperidinium structures, and (ii) through flexible structural motifs in the polymer backbone. Both strategies are based on efficient synthetic routes that avoid noble-metal catalysts and provide versatile opportunities for further molecular design. Using these approaches, several series of AEM materials were synthesized and systematically evaluated with respect to molecular structure, morphology, hydroxide conductivity, hydration behavior, alkaline stability, thermal stability, and mechanical properties. The results show that local molecular flexibility can promote phase separation, facilitate ion transport, and improve the balance between conductivity, stability, and membrane robustness. In addition, selected membranes were evaluated in anion-exchange membrane water electrolyzer (AEMWE) cells, providing initial validation of their practical applicability.
Beyond the development of high-performance AEMs, this work establishes synthetic platforms for studying how subtle variations in side-chain and backbone structure influence membrane properties. The thesis thereby provides new insights into structure–property relationships in AEMs and offers useful guidelines for the rational molecular design of flexible, ether-free membrane materials.
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Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/084a81cd-6597-456d-9239-27772101fe08
- author
- Chen, Si LU
- supervisor
- opponent
-
- Prof. Lammertink, Rob, University of Twente, The Netherlands.
- organization
- publishing date
- 2026
- type
- Thesis
- publication status
- published
- subject
- keywords
- Anion exchange membrane, molecular flexibility, Synthetic strategy, structure-property relationship
- edition
- 1
- publisher
- Department of Chemistry, Lund University
- defense location
- Lecture Hall KC:A, Kemicentrum, Naturvetarvägen 22, Faculty of Engineering LTH, Lund University, Lund.
- defense date
- 2026-06-01 13:00:00
- ISBN
- 978-91-90202-25-8
- 978-91-90202-26-5
- language
- English
- LU publication?
- yes
- id
- 084a81cd-6597-456d-9239-27772101fe08
- date added to LUP
- 2026-04-30 15:59:45
- date last changed
- 2026-05-06 11:24:29
@phdthesis{084a81cd-6597-456d-9239-27772101fe08,
abstract = {{Durable and high-performing anion-exchange membranes (AEMs) are key components in alkaline water electrolyzers and fuel cells. As potentially more sustainable and cost-effective alternatives to proton exchange membrane (PEM)-based systems, AEM-based devices can operate without platinum-group metal catalysts or perfluorinated polymers. However, their broader practical implementation remains limited by insufficient alkaline stability and lower hydroxide conductivity. Moreover, because AEMs must balance multiple interrelated properties for operation in different electrochemical devices, versatile synthetic strategies are particularly important for their development.<br/>Introducing molecular flexibility into AEMs has emerged as an effective strategy to address these limitations. This thesis develops two complementary synthetic platforms for incorporating controlled molecular flexibility into ether-free AEMs: (i) through alkaline-stable flexible spacers in the side chains, with particular attention to 4-position-functionalized piperidinium structures, and (ii) through flexible structural motifs in the polymer backbone. Both strategies are based on efficient synthetic routes that avoid noble-metal catalysts and provide versatile opportunities for further molecular design. Using these approaches, several series of AEM materials were synthesized and systematically evaluated with respect to molecular structure, morphology, hydroxide conductivity, hydration behavior, alkaline stability, thermal stability, and mechanical properties. The results show that local molecular flexibility can promote phase separation, facilitate ion transport, and improve the balance between conductivity, stability, and membrane robustness. In addition, selected membranes were evaluated in anion-exchange membrane water electrolyzer (AEMWE) cells, providing initial validation of their practical applicability.<br/>Beyond the development of high-performance AEMs, this work establishes synthetic platforms for studying how subtle variations in side-chain and backbone structure influence membrane properties. The thesis thereby provides new insights into structure–property relationships in AEMs and offers useful guidelines for the rational molecular design of flexible, ether-free membrane materials.<br/>}},
author = {{Chen, Si}},
isbn = {{978-91-90202-25-8}},
keywords = {{Anion exchange membrane; molecular flexibility; Synthetic strategy; structure-property relationship}},
language = {{eng}},
publisher = {{Department of Chemistry, Lund University}},
school = {{Lund University}},
title = {{Synthetic Strategies toward Arylene-Based Anion Exchange Membranes with High Local Molecular Flexibility}},
url = {{https://lup.lub.lu.se/search/files/248868053/e-nailing_ex_Chen.pdf}},
year = {{2026}},
}