(217d) An Amphiphilic Polysulfone-Graft-Poly(ethylene) Glycol Random Copolymer for Alkaline Exchange Membrane Fuel Cells

The corrosive acidic environment of Proton Exchange Membrane Fuel Cells (PEMFCs) necessitates the use of prohibitively expensive precious metal catalysts, strongly hindering commercial feasibility. The basic environment of an Alkaline Exchange Membrane Fuel Cell (AEMFC), however, provides the potential to use cheap, earth-abundant metal catalysts. Unfortunately, current AEMFCs perform significantly worse than their PEMFC counterparts, due in large part to the poor ionic conductivities of the current alkaline exchange membranes. Our goal is to develop a higher performance alkaline exchange polymer membrane by morphologically tuning the polymer towards more efficient ion transport. To this end, we have developed a novel amphiphilic polymer, quaternary ammonium-functionalized polysulfone-graft-poly(ethylene) glycol (QA PSf-g­-PEG), with the rationale that the hydrophilic PEG grafts co-localizes the ion-conducting quaternary ammonium groups, thereby inducing the formation of efficient ion transport domains.  A fully hydrated QA PSf-g­-PEG film exhibited an ionic conductivity of 35 mS/cm at room temperature, a notable increase over the 20 mS/cm of un-PEGylated films. This conductivity improvement consequently increased the peak power density of the fuel cell from 120 mW/cm² to 185 mW/cm² at 65^oC. We will discuss the synthesis and characterization of the polymers. Experimental Small Angle X-ray Scattering data will be corroborated with coarse grained simulations of the copolymer melt as means to inform structure-property relationships within these films.