Mechanical Properties

Wiederhorn, Sheldon M.; Fields, Richard J.; Low, Samuel R.; Bahng, Gun-Woong; Wehrstedt, Alois; Hahn, Junhee; Tomota, Yō; Miyata, Takashi; Lin, Haiqing; Freeman, Benny D.; Aihara, Shuji; Hagihara, Yukito; Tagawa, Tetsuya

doi:10.1007/978-3-642-16641-9_7

Cited by 3 publications

(2 citation statements)

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“…The pure gas permeabilities of H 2 , CH 4 , N 2 , and O 2 were obtained using a custom-built system based on a constant volume/variable-pressure method. 31 All SDAPP membranes were dried under vacuum overnight followed by an overnight degassing. The upstream pressure was maintained at predetermined set values of 3.0, 6.4, 9.8, 13.0, and 16.6 atm, while the increase in the downstream pressures across the membrane were recorded as a function of time.…”

Section: S S Smentioning

confidence: 99%

Impact of Hydration and Sulfonation on the Morphology and Ionic Conductivity of Sulfonated Poly(phenylene) Proton Exchange Membranes

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Rodriguez

et al. 2019

Macromolecules

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Multiple computational and experimental techniques are used to understand the nanoscale morphology and water/proton transport properties in a series of sulfonated Diels–Alder poly(phenylene) (SDAPP) membranes over a wide range of temperature, hydration, and sulfonation conditions. New synthetic methods allow us to sulfonate the SDAPP membranes to much higher ion exchange capacity levels than has been previously possible. Nanoscale phase separation between the hydrophobic polymer backbone and the hydrophilic water/sulfonic acid groups was observed for all membranes studied. We find good agreement between structure factors calculated from atomistic molecular dynamics (MD) simulations and those measured by X-ray scattering. With increasing hydration, the scattering ionomer peak in SDAPP is found to decrease in intensity. This intensity decrease is shown to be due to a reduction of scattering contrast between the water and polymer and is not indicative of any loss of nanoscale phase separation. Both MD simulations and density functional theory (DFT) calculations show that as hydration levels are increased, the nanostructure morphology in SDAPP evolves from isolated ionic domains to fully percolated water networks containing progressively weaker hydrogen bond strengths. The conductivity of the membranes is measured by electrical impedance spectroscopy and the equivalent proton conductivity calculated from pulsed-field-gradient (PFG) NMR diffusometry measurements of the hydration waters. Comparison of the measured and calculated conductivity reveals that in SDAPP the proton conduction mechanism evolves from being dominated by vehicular transport at low hydration and sulfonation levels to including a significant contribution from the Grötthuss mechanism (also known as structural diffusion) at higher hydration and sulfonation levels. The observed increase in conductivity reflects the impact that changing hydration and sulfonation have on the morphology and hydrogen bond network and ultimately on the membrane performance.

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Section: S S Smentioning

confidence: 99%