Abstract
A novel anion exchange membrane was synthesized via crosslinking of the quaternized polyepichlorohydrin (QPECH) by 1-(3-aminopropyl) imidazole grafted poly(arylene ether ketone) (PAEK-API). While the QPECH provided an excellent ion conductive property, the rigid rod-structured PAEK-API played a reinforcing role, along with providing the high conductivity associated with the pendant API group. The chemical structure of QPECH/PAEK-API membranes was identified by 1H nuclear magnetic resonace spectroscopy. A variety of membrane properties, such as anion conductivity, water uptake, length swelling percentage, and thermal, mechanical and chemical stability, were investigated. The QPECH/PAEK-API1 membrane showed quite high hydroxide ion conductivity, from 0.022 S cm−1 (30 °C) to 0.033 S cm−1 (80 °C), and excellent mechanical strength, associated with the low water uptake of less than 40%, even at 80 °C. Such high conductivity at relatively low water uptake is attributed to the concentrated cationic groups, in a cross-linked structure, facilitating feasible ion transport. Further, the QPECH/PAEK-API membranes showed thermal stability up to 250 °C, and chemical stability for 30 days in a 4 NaOH solution, without significant loss of ion exchange capacity.
Highlights
Fuel cells (FC) are applied in many industrial fields, such as portable devices, vehicles and distributed power generation systems, as a potential eco-friendly power source [1,2,3,4]
PAEK-API was synthesized before crosslinking with PECH
One part of the chloromethyl groups of PECH played a role in the crosslinking reaction with the imidazolium groups of PAEK-API, while the remaining chloromethyl groups of PECH were reacted with 1-methylimidazole for quarternization
Summary
Fuel cells (FC) are applied in many industrial fields, such as portable devices, vehicles and distributed power generation systems, as a potential eco-friendly power source [1,2,3,4]. Great attention has been paid to composite membrane systems containing reinforcing materials to improve the tensile strength of the polymer electrolytes [25,26]. These composite membranes, still often show a weakness associated with incompatibility between the polymer matrix and the supporting materials. As its molecular structure contains carboxyl acid in pendant sites, it can be chemically cross-linked with chloromethyl groups of PECH, and the final crosslinked membrane structure may provide good thermal, mechanical and chemical stability, and high anion conductivity. We used API functional groups, rather than well-known quaternary ammonium groups, for the ion conductive group, as API is expected to show higher anion conductivity and chemical stability in a high pH environment than quaternary ammonium groups, because of the π-conjugated structure of the imidazolium ring
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