Effects of Crosslinker Concentration and Annealing Time on the Creation of Solvent-Free Anion Exchange Membranes

Anion exchange membranes have the potential to replace proton exchange membranes in electrochemical devices, such as hydrogen fuel cells in vehicles. Potential advantages of anion exchange membranes include converting different fuels beyond hydrogen and lower cost without the need for platinum catalysts. Anion exchange membranes may aid world energy demands since fuel cells with anion exchange membranes can be significantly more efficient than internal combustion engine. Anion-powered fuel cells create energy using membranes that enable anion transport to create a flow of electrons. Specifically, anion exchange membranes allow for the transport of hydroxide (OH^-) ions across the membrane from the cathode to the anode. Here, a patent pending material has been discovered that can be made through the process of crosslinking a polyelectrolyte, poly(acrylamide-co-diallyldimethylammonium chloride) (PAAcPDADMAC) with glutaraldehyde (GA) in a solution that is heated in the presence of hydrochloric acid, which acts as a catalyst. Films of varying thicknesses are then synthesized using a film caster. Water uptake, thickness, and ion exchange capacity (IEC) were measured to understand the viability of the films. Varying GA concentration and annealing time were analyzed to determine a processing method to optimize film properties. Increasing GA concentration resulted in an increase in film thickness. Additionally, water uptake was reasonable and weakly dependent on crosslinker concentration. The IEC of the films were also found to be inversely proportional to the GA concentration with values ranging between 0.8 and 1.4 mmol/g while the IEC decreased with longer annealing times. These new findings show potential for these films to be a desirable anion exchange fuel cell membrane in the near future.