Poly(olefin)-Based Anion Exchange Membranes Prepared Using Ziegler–Natta Polymerization

• Published in: Macromolecules Vol. 52; no. 11
• Main Authors: Zhu, Liang, Yu, Xuedi, Peng, Xiong, Zimudzi, Tawanda J., Saikia, Nayan, Kwasny, Michael T., Song, Shaofei, Kushner, Douglas I., Fu, Zhisheng, Tew, Gregory N., Mustain, William E., Yandrasits, Michael A., Hickner, Michael A.
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 29.05.2019
• Subjects: Anions; Electrical conductivity; Electrodes; ENERGY STORAGE; Fuel cells; Membranes
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/acs.macromol.8b02756

Bromoalkyl-functionalized poly(olefin)s were synthesized by copolymerization of 4-(4-methylphenyl)-1-butene with 11-bromo-1-undecene using Ziegler–Natta polymerization. The resulting bromoalkyl-functionalized poly(olefin)s were converted to quaternary ammonium-containing anion-conductive copolymers by reacting the pendant bromoalkyl group with trimethylamine or a custom-synthesized tertiary amine containing pendant quaternary ammonium moieties. Poly(olefin)-based AEMs with three cations per side chain showed considerably higher hydroxide conductivities, up to 201 mS/cm at 80 °C in liquid water, compared to that of samples with only one cation per bromoalkyl site (68 mS/cm, 80 °C, liquid water), likely due to phase separation in the triple-cation structure. More importantly, triple-cation side-chain poly(olefin) AEMs exhibited higher hydroxide conductivity under relative humidity conditions (50%–100%) than typical AEMs based on benzyltrimethylammonium cations. Here, the triple-cation the triple-cation side-chain poly(olefin)-based AEM exhibited an ionic conductivity as high as 115 mS/cm under 95% RH at 80 °C and 11 mS/cm under 50% RH at 80 °C. In addition to high ionic conductivity, the triple-cation side-chain poly(olefin) AEMs exhibited good chemical and dimensional stability. High retention of ionic conductivity (>85%) was observed for the samples in 1 M NaOH at 80 °C over 1000 h. Based on these high-performance poly(olefin) AEMs, a fuel cell with a peak power density of 0.94 W cm–2 (1.28 W cm–2 after iR correction) was achieved under H2/O2 at 70 °C. The results of this study suggest a new, low-cost, and scalable route for preparation of poly(olefin)-based AEMs for anion exchange membrane applications.