Designing Anion-Exchange Ionomers with Oriented Nanoscale Phase Separation at a Silver Interface

Abstract

Performance of polymer electrolyte-based energy systems is significantly impacted by transport within the electrode catalyst layer, where ionomer thin films coat catalyst particles. Proton exchange ionomer thin films have been thoroughly characterized, but few studies have critically examined anion-exchange ionomer (AEI) thin films. Further, none have reported nanoscale phase separation for hydrocarbon AEIs, which is critical to mitigate transport resistances. In this work, a set of hydrocarbon-based AEIs with nanoscale phase separation are developed from tunable block copolymer systems composed of polyisoprene (PIp) and polychloromethylstyrene (PCMS). The effect of the PIp/PCMS ratio, architecture, and thickness on the thin-film morphology of the neutral block copolymer precursors on silicon and silver substrates is investigated using grazing-incidence small-angle X-ray scattering (GISAXS) and atomic force microscopy (AFM). AEIs are prepared by quaternizing with trimethylamine or methylpiperidine and their cation-dependent morphology is characterized at 60 °C and 95% RH. A perpendicularly aligned morphology is observed on silver, while no phase separation is observed on silicon, indicating that silver–polymer interfacial interactions drive phase separation. After quaternization, dipole–dipole interactions induce some disorder, but nanoscale phase separation is still maintained. GISAXS patterns are modeled using a Unified Fit approach to understand water uptake and swelling, and recommendations for AEI design are presented.

Effect of Block Length on the Properties of Multiblock Polysulfone-Poly(diallylpiperidinium hydroxide) Anion Exchange Membranes

“…Multiblock is another type of copolymer architecture that has been shown to produce phase-separated membranes. − An advantage of designing multiblock hydrophilic–hydrophobic copolymers is that high molecular weight copolymers can be prepared from a range of molecular weights in the component materials. Research conducted on multiblock polysulfone (PSf) materials has produced copolymers from a variety of bisphenol monomers. − Manipulation of the multiblock composition and the molecular weight of the component segments can tune the microphase separation .…”

Zeroth-Order Nucleation Transition under Nanoscale Phase Separation

“…Recently, the possibility of superfluid dislocations inside quantum crystals has been discussed [28][29][30]. Different types of nanoscale phase separation occur in electrolytes [31][32][33][34][35].…”

Investigation of Ionomer and Catalyst (Co3O4, Mn3O4, or MnO2) Interactions Using a Polyethylene Midblock Copolymer in Anion Exchange Water Electrolyzers to Understand Performance and Durability

“…This material was varied for both the AEI or the AEM of an AEMWE and the optimized polymers investigated by us previously are used in this study. 27,32,[34][35][36] To keep the system relatively simple and focus on the catalyst-AEI interaction, this study was confined to AEIs and AEMs using a bare Ni-foam as an anode catalyst with no microporous layer (MPL). Each catalyst were studied with varying loadings (0.5, 2.5, and 4.5 mg cm −2 on a Ni-foam substrate) and a constant ionomer content and identical membrane.…”

“…[23][24][25][26] Buggy et al studied a chemistry-structureproperty relationship of block copolymer anion exchange ionomer (AEI) on silver surface to design tunable ionomer for AEM device applications. 27 And Gupta et al implemented the block copolymer based AEIs in AEMWE device studies, where a combination of polystyrene-b-poly (ethylene/butylene)-b-polystyrene block copolymer and NiCo 2 O 4 electrocatalyst resulted in 10 mg cm −2 NiCO 2 O 4 owning higher OER activity than 2 mg cm −2 IrO 2 . 28 While performance has been emphasized in the past, the demonstration of practical durability is still needed to commercialize this technology.…”