Polarization modulation-infrared reflection-absorption spectroscopy (PM-IRRAS) and neutron reflectometry (NR) of sulfonated poly[ether ether ketone] (SPEEK), on both Pt and SiO2 surfaces facilitate development of advanced catalyst/ionomer interfacial models. PM-IRRAS, in conjunction with density functional theory-calculated normal mode analysis, enables determination of how ionomer functional groups self-assemble on surfaces. NR allows for the determination of ionomer layer thicknesses and phase segregation in ionomer thin films. Preliminary X-ray reflectometry suggests that the SPEEK spin coated onto SiO2 surfaces forms a 2-layer ionomer structure. The top layer is less dense and thicker than the layer adjacent to the substrate. NR data of SPEEK on both Pt and SiO2 has been obtained and is currently being fitted. Transmission FT-IR spectra of SPEEK at varying states-of-hydration show different water sorption properties versus Nafion, due to its shorter hydration channels and dead-end pathways. We expect this to lead to differences in polymer interfacial structures compared to those found for Nafion, including state-of-hydration and number of layers at the respective interfaces. PMIRRAS elucidates what effect the more rigid, aromatic backbone will have on SPEEK self-assembly.

Infrared and neutron reflectometry of sulfonated poly(ether ether ketone) interfaces with Pt and SiO2

249th National Meeting (2015)

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