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

• DOI: 10.1021/acs.macromol.8b02355
• Publication Date: 2019-02-20T21:16:46Z
• Authors: Jong Yeob Jeon; Sungmin Park; Junyoung Han; Sandip Maurya; Angela D. Mohanty; Ding Tian; Nayan Saikia; Michael A. Hickner; Chang Y. Ryu; Mark E. Tuckerman; Stephen J. Paddison; Yu Seung Kim; Chulsung Bae
• Keywords: Polystyrene; Thermoplastic elastomer

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