Abstract
Novel proton exchange membranes (PEMs) based on graft copoly(arylene ether sulfone)s with enhanced phase-separated morphology were prepared using atom transfer radical polymerization (ATRP). A series of PEMs with different graft lengths and sulfonation degrees were prepared. The phase-separated morphologies were confirmed by transmission electron microscopy. Among the membranes prepared and evaluated, PAESPS18S2 exhibited considerably high proton conductivity (0.151 S/cm, 85 °C), benefitting from the graft polymer architecture and phase-separated morphology. The membranes also possessed excellent thermal and chemical stabilities. Highly conductive and stable copoly(arylene ether sulfone)-based membranes would be promising candidates as polymer electrolytes for fuel cell applications.
Highlights
Proton exchange membrane (PEM), an essential component of proton exchange membrane fuel cells (PEMFCs), is considered to be an electrolyte for transporting protons from anode to cathode and as a separator to prevent the mixing of hydrogen and oxidant [1,2]
Polystyrenes were successfully grafted onto poly(arylene ether sulfone) backbone by the atom transfer radical polymerization (ATRP)
A morphological study using TEM indicated that enhanced enhanced phase-separated morphology and interconnected ionic channels were formed in these poly(arylene ether sulfone) (PAES)
Summary
Proton exchange membrane (PEM), an essential component of proton exchange membrane fuel cells (PEMFCs), is considered to be an electrolyte for transporting protons from anode to cathode and as a separator to prevent the mixing of hydrogen and oxidant [1,2]. Extensive efforts have been devoted to developing alternative hydrocarbon-based PEMs to overcome the drawbacks of the perfluorosulfonic acid membranes [1,5] Among these materials, sulfonated poly(arylene ether sulfone) is widely considered as a potential alternative due to its good thermal stability, strong mechanical properties, and excellent chemical stability. The property difference between a hydrophobic polymer backbone and hydrophilic sulfonic acid side chain leads to phase separation morphology of the PEM. Zhang et al [21] reported the ATRP graft reaction of a series of poly(vinylidene fluoride)-g-sulfonated polystyrene (PVDF-g-SPS) graft copolymers This graft copolymer morphology contributed positively to a high ion exchange capacity (IEC, 2.75 mmol/g) and resistance to excessive water swelling, which yielded notably higher proton conductivity. Studies related to polysulfone-based PEMs prepared via ATRP are still rare, and properties including proton conductivity and water uptake need to be further improved. The ion exchange capacity, water uptake, and proton conductivity of the PEMs were measured and compared to reveal the structure-property relationships in this class of PEMs
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