Synthesis and properties of anion conductive ionomers containing fluorenyl groups for alkaline fuel cell applications

Abstract

A series of anion conductive aromatic ionomers, poly(arylene ether)s containing different polymer backbones and quaternized ammonio-substituted fluorenyl groups, were synthesized via nucleophilic substitution polycondensation, chloromethylation, quaternization, and the subsequent ion exchange reactions. The ion exchange capacity (IEC) of the ionomers was controlled to be from 0.68 to 2.54 meq. g À1 by the chloromethylation reaction conditions. The designed chemical structures were wellcharacterized by the 1 H NMR spectra. The ionomers provided ductile and transparent membranes. The ionomer membranes were thermally stable up to 180 C under nitrogen and mechanically stable with 48 MPa of the maximum stress at 80 C and 60% RH (relative humidity). High hydroxide ion conductivity up to 50 mS cm À1 was achieved at 30 C in water for the ionomer membrane bearing sulfone/ketone structures and the highest IEC (2.54 meq. g À1 ). The membranes were durable in hot water (80 C) for 1000 hours. These properties of the ionomer membranes seem promising as an anion exchange membrane for alkaline fuel cells.

Phenyltrimethylammonium Functionalized Polysulfone Anion Exchange Membranes

“…The decomposition temperature of the polymer backbone was similar to that of the parent polymer, 7 suggesting that the decomposition of the quaternary ammonium groups did not trigger degradation of the polymer backbone, which was observed in some aromatic AEMs. 50 As mentioned above, the degradation of PTMA functionalized 4 membranes occurs under high pH conditions probably via (i) Hoffmann elimination and (ii) direct nucleophilic substitution. 19,22,23 To further evaluate the stability and degradation mechanism of the 4 membranes, 4(X50) membrane with IEC of 1.32 mequiv/g was treated with 4 M NaOH aqueous for different exposure times.…”

Densely quaternized anion exchange membranes synthesized from Ullmann coupling extension of ionic segments for vanadium redox flow batteries

“…The final quaternization step keeps lowering the initial decomposition temperature to~190°C while maintaining the two-stage decomposition profile of brominated samples. The first stage can be attributed to the decomposition of the QA groups, while the second stage is the decomposition of the aromatic backbones [21,27]. The 5% weight-loss temperatures (T d-5% ) for QA-OMPFEK-20 and QA-TMPFEK-40 are 236.0°C and 250.6°C, respectively.…”

“…For chloromethylation route, the PAE precursors should contain electron-rich phenyl rings that are not connected to any electron-withdrawing group such as ketone or sulfone. Nevertheless, the chloromethylation requires the use of carcinogenic chloromethylation reactant (e.g., chloromethyl methyl ether), and the reaction degree is hard to control, with the risk of cross-linking [27]. These drawbacks hindered the employment of chloromethylation in the design and preparation of high performance AEMs.…”

Direct oxidation alkaline fuelcells: from materials to systems

“…However, the Friedel-Crafts chloromethylation reaction of this kind of polymer takes approximately one week and there are risks of cross-linking to become insoluble. [126][127][128] Tanaka et al recently synthesised a block poly (arylene ether)s anion exchange membrane with a excellent conductivity of 0.144 S cm À1 at 80 C. 127 The fuel cell performance using hydrazine and pure oxygen reached 297 mW cm À2 . Kim from Los Alamos National Laboratory reported that poly (phenylene) based AEM prepared by Sandia National Laboratory using aminated tetramethoxyphenylporphirine (TMPP) obtained good chemical and mechanical stability (stable >670 h at 60 C in 4 M NaOH), due to the wholly aromatic structure.…”