The development and implementation of high-throughput tools for discovery and characterization of proton exchange membranes

The need for sustainable energy use has motivated the exploration of renewable alternative fuels and fuel conversion technology on a global scale. Fuel cells, which convert chemical energy directly into electrical energy with high efficiency and low emissions, provide a promising strategy for achieving energy sustainability. The current progress in fuel cell commercialization is mainly in portable and stationary applications, but fuel cell technology for transportation applications, which make up a substantial portion of the global energy market, have seen little commercial success. Proton exchange membrane fuel cells (PEMFCs) have high potential for addressing the future energy needs of the transportation energy sector. However, one of the prevailing limitations of the PEMFC is the availability of high-performance, cost-effective electrolyte materials. These materials may be realized in the near future by developing multifunctional polymer blends targeted at specific performance capabilities. Since the number of available polymer combinations and numerous processing variations provide an almost infinite source of PEMFC membrane candidates, efficient methods of discovering high-performance PEM materials are necessary. Combinatorial methods meet these needs using gradient or discrete techniques to capture process variations such as annealing temperature, thickness, and chemical composition into a single polymer sample that serves as a library of materials. To characterize these heterogeneous samples for fuel cell performance, specific high-throughput measurement techniques are necessary. In this work, a high-throughput mass transport assay (HT-MTA) has been developed to characterize water flux and permeability at multiple sample locations in parallel. The functionality of HT-MTA was evaluated using standard NafionRTM films and a model semi-interpenetrated polymer network with commercial polyvinylidine fluoride as the host matrix for a proprietary polyelectrolyte supplied by Arkema, Inc. Although mass transport values were generally lower than reported literature values, pervaporation experiments showed that HT-MTA could be used to effectively screen and optimize relative water transport characteristics in PEMs. To further demonstrate the utility of HT-MTA, the instrument was incorporated into the lab's current high-throughput characterization toolset and used to investigate the mechanisms and effects of rapid free radical degradation of NafionRTM membranes based on various concentrations of H2O2 and Fe2+. The results showed that changes in Nafion'sRTM mechanical, conductive, and water transport properties were strong functions of H2O 2, and that maximal degradation could be achieved around 50 ppm Fe 2+. Furthermore, by including chemical composition analysis techniques in the characterization toolset, the dominating free radical degradation pathways could be deduced. These results are promising for later correlating rapidly aged degradation experiments to in situ fuel cell lifetime testing which is both time-intensive and costly.;The high-throughput toolset was also used to develop a novel optimized blend consisting of polyetherimide (PEI), a low-cost high performance resin, and sulfonated PEI (S-PEI) made using a relatively mild post sulfonation reaction with trimethylsilyl chlorosulfonate. The effects of blend composition and thermal annealing on film performance were evaluated and the polymer system was shown to have optimal mechanical and ion-conducting properties between 20--30 wt% S-PEI in the unannealed state. Although the properties of the proposed PEI-based polymer system were below PEMFC performance standards, a PEI film with superior mechanical properties was discovered and should prove to be useful in other applications. In general, this work shows promising results for efficiently developing advanced polymer materials using high-throughput screening techniques.