Synthesis of Aromatic Anion Exchange Membranes by Friedel–Crafts Bromoalkylation and Cross-Linking of Polystyrene Block Copolymers

Journal Article · Wed Feb 20 00:00:00 EST 2019 · Macromolecules

DOI:https://doi.org/10.1021/acs.macromol.8b02355· OSTI ID:1503188

Jeon, Jong Yeob ^[1]; Park, Sungmin ^[1]; Han, Junyoung ^[1]; Maurya, Sandip ^[2]; Mohanty, Angela D. ^[1]; Tian, Ding ^[1]; Saikia, Nayan ^[3]; Hickner, Michael A. ^[3]; Ryu, Chang Y. ^[1]; Tuckerman, Mark E. ^[4]; Paddison, Stephen J. ^[5]; Kim, Yu Seung ^[2]; Bae, Chulsung ^[6]

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1. Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Chemistry and Chemical Biology
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
3. Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering
4. New York Univ. (NYU), NY (United States). Dept. of Chemistry. Courant Inst. of Mathematical Sciences; NYU Shanghai (China). NYU-ECNU Center for Computational Chemistry
5. Univ. of Tennessee, Knoxville, TN (United States). Dept. of Chemical & Biomolecular Engineering
6. Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Chemistry and Chemical Biology. Dept. of Chemical and Biological Engineering

Elastomeric anion exchange membranes (AEMs) were prepared here by acid-catalyzed Friedel–Crafts alkylation of the polystyrene block of polystyrene-b-poly(ethylene-co-butylene)-b-polystyrene (SEBS) using bromoalkylated tertiary alcohols and triflic acid as a catalyst, followed by amination with trimethylamine. This simple one-step bromoalkylation allowed convenient control of both the degree of functionalization and cation tether length by changing the molar ratio and the structure of the bromoalkylated tertiary alcohol. The resulting quaternary ammonium-functionalized ionic triblock SEBS copolymers showed a microphase-separated morphology on the 35 nm length scale. A series of AEMs with different ion exchange capacities and ion tether lengths were systematically investigated by comparing swelling and anion conductivity. Because the SEBS AEMs showed high swelling and low dimensional stability in water due to the rubbery nature of SEBS, the hard segment PS units were cross-linked by 1,6-hexanediamine for practical use. The cross-linking of SEBS AEMs reduced water uptake significantly (e.g., 155% vs 28%) and enhanced their mechanical properties. Because the backbone of the SEBS AEMs are composed of all carbon–carbon bonds, they showed good alkaline stability, preserving their IEC and OH– conductivity after testing in a 1 M NaOH solution at 80 °C for 500 h. Alkaline membrane fuel cell performance was evaluated with the cross-linked SEBS AEM, and a peak power density of 520 mW/cm² was achieved at 60 °C under H₂/O₂ conditions.

• Research Organization: Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Rensselaer Polytechnic Inst., Troy, NY (United States)
• Sponsoring Organization: National Science Foundation (NSF) (United States); USDOE Advanced Research Projects Agency - Energy (ARPA-E); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Fuel Cell Technologies Office (EE-3F); USDOE Office of Science (SC)
• Grant/Contract Number: 89233218CNA000001; AC02-06CH11357; AR0000769
• OSTI ID: 1503188
• Alternate ID(s): OSTI ID: 1513019
• Report Number(s): LA-UR--18-28671
• Journal Information: Macromolecules, Journal Name: Macromolecules Journal Issue: 5 Vol. 52; ISSN 0024-9297
• Publisher: American Chemical Society
• Country of Publication: United States
• Language: English

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY