New siloxane-based copolymers for use in anion exchange membrane fuel cells

• Anion exchange siloxane-based copolymer membrane was prepared.
• Crosslinked siloxane copolymers showed enhanced thermal stability and high IEC.
• High hydroxide conductivity was obtained at DPhQA-DM 16L copolymer membrane.

New anion exchange membranes made by crosslinking poly(diphenyl-co-dimethylsiloxane) (DPh-DM) copolymers and incorporating quaternary ammonium groups via chloromethylation and alkalization to afford DPh-DM with quaternary ammonium groups (DPhQA-DM) for use in anion exchange membrane fuel cells (AEMFCs). The membranes were characterized by using Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), water uptake, swelling, ion exchange capacity and hydroxide conductivity. The hydroxide conductivities of the DPhQA-DM copolymers were found to be greatly dependent on the amount of crosslinker used, molecular weight and the number of phenyl groups. DPhQA-DM 16L copolymer membrane was found to have a high hydroxide conductivity of 45 mS/cm at 80 °C. In addition, the membrane exhibited high ion exchange capacity and water uptake, as well as good thermal properties.