A complete investigation of poly(2,6-dimethyl-1,4-phenylene) AEMs with different quaternary ammonium groups is provided comparing the properties and fuel cell performance.

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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.

At present, liquid membranes, ion-exchange membranes and fixed carrier membranes are the three popular facilitated transport membranes for CO2 separation. We report a method to combine their advantages and overcome their deficiencies.

A PVAm-HT membrane is fabricated by establishing a hydrotalcite (HT) channel in a polyvinylamine (PVAm) fixed carrier membrane. The flexible PVAm fixed carrier membrane material as a matrix membrane is beneficial to get high permeance. Simultaneously, the HT channels can be used as high-speed facilitated transport channels, in which the movable carbonate can actively meet CO 2 and help to increase the CO 2 /N 2 selectivity of membranes as in liquid membranes or in ion exchange membranes. Moreover, the unobstructed HT channels are conducive to transport CO 2 rapidly and they can increase the chain spacing of polymers; these are beneficial to further enhance the permeance of membranes. In addition, the charged layers of HT provide necessary stability for movable carriers due to the electrostatic attraction. Thus, the PVAm-HT membrane obtains high permeance and high selectivity, as well as good stability. The CO 2 permeance of the PVAm-HT membrane reaches 3187 GPU and the CO 2 /N 2 selectivity of the PVAm-HT membrane reaches 296 at 0.11 MPa.Scheme 1 Schematic of CO 2 transport mechanisms in different membranes, (a) Na 2 CO 3 liquid membrane; (b) ion-exchange membrane; (c) fixed carrier membrane; (d) fixed carrier membrane containing high-speed facilitated transport channels.This journal is

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