Facile Preparation of an Ether-Free Anion Exchange Membrane with Pendant Cyclic Quaternary Ammonium Groups

Abstract

Ether-bond-free polyfluorene (PBF) anion exchange membranes (AEMs) containing flexible alkyl pendent chains terminated with piperidinium cations were prepared via one-pot, superacid-catalyzed polycondensation and a subsequent quaternization reaction. Hydrophilic and hydrophobic microphase segregation was observed in all AEMs. The hydroxide conductivity of PBF2-Br reaches up to 86 mS cm–1 at 80 °C, and 1H NMR showed no measurable degradation after alkaline treatment in aqueous NaOH (1 M) solution for 1200 h at 80 °C. Besides, a peak power density of 410 mW cm–2 was achieved at 60 °C for an alkaline fuel cell using the selected PBF1-OH (OH– form) as AEM.

Rational molecular design of anion exchange membranes functionalized with alicyclic quaternary ammonium cations

“…The conductivity results are in good agreement with previous findings on AEMs with DMP and ASU cations directly attached to the poly(arylene alkylene)s. 57 Beside the higher IEC and water uptake, the less bulky DMP cations might also facilitate ion clustering during casting, thus promoting phase separation and ion transport. The conductivity of PDPF-DMP was comparable or significantly higher than with that of AEMs with similar or higher IEC (Table 2), [46][47][48]53,58 demonstrating the advantages of the present molecular design on the hydroxide conductivity of AEMs.…”

“…39 These findings have motivated quite extensive research on AEMs functionalized with piperidine-based cations in recent years. [44][45][46][47][48][49][50] However, when these cations are directly incorporated in stiff aromatic polymer backbones, the alkaline stability is significantly reduced in relation to that of the model compounds. 27,28 This has been explained by a distortion of the alicyclic rings by the stiff backbones, which facilitates degradation by Hofmann elimination.…”

Overview: State-of-the Art Commercial Membranes for Anion Exchange Membrane Water Electrolysis

“…A second polymer type is prepared by Friedel-Crafts reaction between aromatic monomers and aliphatic ketones, e.g., CF 3 -CO-(CH 2 ) 5 -Br [48,49]. The third class of polymer backbones is based on polybenzimidazole.…”

Progress of Alkaline Anion Exchange Membranes for Fuel Cells: The Effects of Micro-Phase Separation

“…In recent years, various AEMs based on aliphatic or aromatic polymers [such as poly(sulfone)s, poly(arylene ether)s, poly(phenylene)s, poly(styrene)s, polypropylene, poly(phenylene oxide)s, poly(olefin)s, poly(arylene piperidinium), and poly(biphenyl alkylene)s] with different cationic groups (such as quaternary ammonium, guanidinium, imidazolium, pyridinium, tertiary sulfonium, spirocyclic quaternary ammonium, phosphonium, phosphatranium, phosphazenium, metal-cation, benzimidazolium, and pyrrolidinium) have been synthesized to prepare AEMs with high conductivity and excellent alkaline stability (Choi et al, 2005;Gu et al, 2009;Kong et al, 2009;Pan et al, 2010b;Zhang et al, 2010Zhang et al, , 2012Kim et al, 2011;Lin et al, 2011Lin et al, , 2013aDöbbelin et al, 2012;Zha et al, 2012;Arges et al, 2014;Pham and Jannasch, 2015;Xue et al, 2017;Chen et al, 2018;Peng et al, 2018;Zhu et al, 2018;Ren et al, 2019;Wang et al, 2019). Although the performance of AEMs was greatly enhanced during the past few years, the foundational properties of AEMs are not comparable to those of PEMs (such as Nafion) due to the intrinsic low mobility of OH − and the well-known base-induced decomposition of organic cations as well as polymer backbones (Tanaka et al, 2011;Noonan et al, 2012;Qiu et al, 2012;Kim et al, 2017;Hao et al, 2018).…”