title: Facilitating Anion Transport in Polyolefin-Based Anion Exchange Membranes via Bulky Side Chains.
abstract: Highly anion-conductive polymer electrolyte membranes with excellent alkaline stabilities for fuel cell applications were prepared. Thus, a series of polyolefin copolymers with poly(4-methyl-1-pentene) (PMP) moieties containing bulky side chains and side-chain quaternary ammonium (QA) groups were prepared through copolymerization with a Ziegler-Natta catalyst and subsequent quaternization. The separation of hydrophilic microphase and hydrophobic microphase was induced by PMP bulky side chains, and then well-connected ionic domains were formed. This result was confirmed by AFM (atomic force microscopy) and SAXS (small-angle X-ray scattering) analyses. It was discovered that well-defined ionic domains of the PMP-TMA-x (TMA, trimethylamine) membranes depended on the content of PMP moieties. The well-defined ionic domains enhanced the hydroxide conductivity of the PMP-TMA-x membranes despite their lower water uptake (WU) as compared to polypropylene (PP)-containing membranes (PP-TMA-x). The PMP-TMA-41 membrane showed the highest ionic conductivity value (43 mS/cm) while maintaining low WU (29.2 wt %) at room temperature. The membranes mostly preserved (>93.0%) their initial hydroxide conductivity after alkaline treatment (10 M aqueous NaOH, 80 °C, 700 h), thereby revealing desirable alkali stability characteristics. Presumably, the nucleophilic attack from hydroxide or water in the cationic center is inhibited by long alkyl spacers (-CH2-)n (n = 9) which are located between the cation groups and the polymer backbone.
authors.affiliation: College of Materials Science and Engineering, Beijing Institute of Petrochemical Technology , Beijing, 102617, China.
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.affiliation: College of Materials Science and Engineering, Beijing Institute of Petrochemical Technology , Beijing, 102617, China.
authors.forename: Chunrong
authors.initials: C
authors.lastname: Shan
authors.affiliation: State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences , Taiyuan, 030001, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences , Taiyuan, 030001, China.
authors.forename: Jiayou
authors.initials: J
authors.lastname: Liao
authors.affiliation: State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences , Changchun, 130022, China.
authors.forename: Quan
authors.initials: Q
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University , Xi'an, 710072, China.
authors.forename: Meng
authors.initials: M
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Solidification Processing, Northwestern Polytechnical University , Xi'an, 710072, China.
authors.forename: Yiguang
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Materials Science and Engineering, Advanced Materials Processing and Analysis Center, University of Central Florida , Orlando, Florida 32816, United States.
authors.forename: Linan
authors.initials: L
authors.lastname: An
authors.affiliation: State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences , Taiyuan, 030001, China.
authors.forename: Nanwen
authors.initials: N
authors.lastname: Li
keywords: alkaline stability; anion conductivity; anion exchange membranes; phase separation; poly(4-methyl-1-pentene)