Bond breaking following H radical attachment in in sulfonated polyethersulfone; model calculations for fuel cell membrane decomposition

Jacksi, Helin, and Jonathan Stevens

~~Polymer Electrolyte Membrane Fuel Cells (PEMFCs) are targeted to be used for portable and stationary fuel cell applications. Sulfonated PSU (sulfonated polyethersulfone) membranes can be potential candidates for these fuel cell membrane applications. This study focused on a model molecule derived from the PSU polymer, called PSU1, and how it behaves in an environment of hydrogen radicals. In a previous study, the attachment of hydrogen to different sites on the aromatic ring of the model molecule was observed and the enthalpies of each attachment were calculated by using the M062X method. From these results, it was hypothesized that the existing substituents on the aromatic ring would break off after hydrogen attachment. This current study focuses on the bond breakage of the substituents on two specific sites.  In order to study the these bond-breaking,s the transition states of each reaction of detachment were optimized using the M062X method. Enthalpies of reaction for the complete bond breakages were also calculated. These results suggest that the PSU1 model molecule readily undergoes bond-breaking, indicating a means of degradation for sulfonated polyethersulfone membranes.