Triphenyl amine containing sulfonated aromatic polyimide proton exchange membranes

• Triphenylamine containing sulfonated polyimides (SPIs) were synthesized.
• SPIs showed high proton conductivities (up to 207 mS cm−1 at 80 °C in water).
• Good phase-separated morphology and low fuel crossover was observed for these SPIs.

A series of new sulfonated co-polyimides (co-SPI) were prepared by the polycondensation reaction of two diamines namely; 4,4′-diaminostilbene-2,2′-disulfonic acid (DSDSA) and 4,4′-diaminotriphenylamine (DATPA) with 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA). All the copolymers showed good solubility and flexible membranes were obtained from their DMAc solution. The transmission electron microscopy (TEM) of the polymers revealed microphase separated morphology with well-dispersed hydrophilic (around 5–100 nm) and hydrophobic domains. The SPI membrane DTN-80 (80% degree of sulfonation) with ionic exchange capacity (IECw) of 2.74 mequiv g−1 showed significantly higher proton conductivity (207 mS cm−1) at 80 °C in water as compared to the perfluorinated Nafion® 117 (135 mS cm−1) under similar test conditions. All these co-SPI membranes showed lower oxygen permeability (for DTN-80, PO2 = 0.9 barrer) than Nafion® 117 (PO2 = 3.6 barrer).

Figure optionsDownload as PowerPoint slide