Cross-linked membranes with a macromolecular cross-linker for direct methanol fuel cells

Abstract

With the goal of reducing water swelling and methanol permeability in sulfonated proton exchange membranes (PEM), bromomethylated poly(ether ether ketone) was synthesized and used as a macromolecular cross-linker. The cross-linking reaction was performed at 195 C for 5 h and resulted in cross-linked membranes with high cross-linked density. Compared to the pristine membrane, the cross-linked membranes displayed greatly reduced water uptake and methanol permeability. Other properties of the cross-linked membranes, including proton conductivity, mechanical properties, and oxidative stability, were also investigated and compared with the pristine membrane. All the results indicated that the novel macromolecular cross-linker and the resulting cross-linked membranes are promising for fuel cell applications.

Building bridges: Crosslinking of sulfonated aromatic polymers—A review

“…An in-depth theoretical analysis suggested that higher acid content does not always result in higher proton conductivity [135]. In addition, the degree of crosslinking plays an important role in optimized properties of SAP and should be carefully controlled and optimized [71,109]. A too small degree of crosslinking is not sufficient to maintain the desired dimensional, mechanical and thermal stability of high IEC SAP.…”

“…Other kinds of XL reactions based on pseudo Friedel-Crafts alkylation were reported: the crosslinking reaction occurred between benzylic alcohol and a phenyl ring linked to phosphazene backbone [108] or bromomethylated SPEEK [109] under acidic or heating conditions. XL SPEEK with bromomethyl groups shows water uptake, methanol permeability and proton conductivity reduced with respect to those of pristine SPEEK, but the thermal stability was also unexpectedly slightly lower due to remaining CBr bonds after crosslinking.…”

“…Occasionally, crosslinking can modify the properties of SAP in an unexpected way, for example, increasing the water uptake [80], decreasing the thermal stability [109], inducing brittleness [23], reducing the proton conductivity even without consuming -SO 3 H groups [91,92] or enhancing the proton conductivity even with loss of -SO 3 H groups. These results depend on the experimental conditions during the crosslinking reaction or the micro-structure after crosslinking.…”

Crosslinked poly(vinylbenzyl chloride) with a macromolecular crosslinker for anion exchange membrane fuel cells

“…comparison with a macromolecular crosslinker [21], but the later was seldom reported in the field of AEMs.…”

Regulation of micromorphology and proton conductivity of sulfonated polyimide/crosslinked PNIPAm semi‐interpenetrating networks by hydrogen bonding

“…S1. Compared with pristine SPI, the Young's modulus of SPI‐cPNIPAm semi‐IPN membranes increases after the incorporation of semi‐IPN cPNIPAm networks, while the tensile strength and elongation at break are decreased because of the crosslinking structure which results in a decline of elasticity of the semi‐IPN membranes . However, the modulus of SPI‐25‐cPNIPAm is obviously reduced due to the phase separation between SPI and cPNIPAm.…”