Solution-blended sulfonated polyphenylene and branched poly(arylene ether sulfone): Synthesis, state of water, surface energy, proton transport, and fuel cell performance. (3rd January 2019)

• Record Type: Journal Article
• Authors: Motealleh, Behrooz; Huang, Fei; Largier, Timothy D.; Khan, Wayz; Cornelius, Chris J.
• Is Part Of: Polymer. Volume 160(2019)
• Page Start: 148
• Page End: 161
• Publication Date: 2019-01-03
• Subjects: Ionomer blends -- Ion transport and state-of-water -- Hydrogen fuel-cell; Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; 547.7
• DOI: 10.1016/j.polymer.2018.11.045
• Languages: English
• ISSNs: 0032-3861

Abstract

Abstract: A poly(arylene ether sulfone) (PAES) was synthesized with a sulfonated poly(phenyl sulfone) side-chain (sB) to create a branched sBPAES ionomer. This sBPAES ionomer was solution blended with sulfonated polyphenylene (sPP). The sulfonated side-chain dramatically improved miscibility between these distinctly different ionomers. This functional group facilitated their solution-casting into robust films that were flexible and tough. Ionomer film proton conductivity, water uptake, density, state-of-water, contact angle, surface energy, wide angle x-ray scattering, and hydrogen fuel-cell function were studied based upon blend concentration. Results showed that sPP blended with 5 wt% sBPAES had a relative free water content that increased by 97% as compared to unblended sPP. Ionomer blends containing 10 wt% sBPAES reduced the film's water uptake by 37.5% and only caused a 3.3% decrease in proton conductivity from 97.5 to 94.3 mS/cm. The relative free water concentration improved within the blend up to 10 wt% sBPAES. These improvements were attributed to changes in ion clustering noted using wide angle x-ray scattering. The film's apparent water contact angle revealed that introducing 10 wt % sBPAES into sPP lowered its surface energy from 27.2 mJ/m 2 to 24.3 mJ/m 2 . This led to a higher membrane-electrode interfacial resistance for these ionomer-blended films. An optimal ionomer-blend containing 5 wt% sBPAES had a H2 /O2 peak-power output of 630 mW/cm 2 at 1490 mA/cm 2, which was greater than its unmodified sPP version of 570 mW/cm 2 and 1220 mA/cm 2 . Graphical abstract: Highlights: sPP:sBPAES ionomer-blends decreased water uptake. sPP conductivity increased from 94 mS/cm to 101 mS/cm by adding 5 wt% sBPAES. Ionomer-blends were modeled using a modified Nernst-Einstein Equation. Free water in sPP increased from 10.3% to the 16% by adding 5 wt% of sBPAES. PAES-sSPU-sPP peak-power was 630 mW/cm 2 versus SPP at 570 mW/cm 2 .