Synthesis and Properties of Quaternary Phosphonium-based Anion Exchange Membrane for Fuel Cells

Quaternary phosphonium-based polyelectrolyte was synthesized from bromomethylated poly（2,6-dimethyl-1,4- phenylene oxide） （BPPO） by functionalization with tris（2,4,6-trimethoxyphenyl） phosphine （TTMPP）. Typically, excellent solubility of the polyelectrolyte in polar solvents, such as NMP and DMSO, allowed a solution-casting strategy for preparation of anion exchange membrane （AEM） with properly ordered hydrophilic/hydrophobic nano-scale phase separation morphology, which was visible in atomic force microscopic phase images. Accordingly, the optimized ionmeric AEM exhibited excellent hydroxide conductivity of 110 mS/cm at 70℃, but extremely re- stricted linear expansion ratio of below 7% at the same temperature. Additionally, such membrane could maintain flexibility and conductivity after an immersion treatment in 1 mol/L NaOH solution at 60 ℃ for about 100 h, im- plying its potential in alkaline fuel cells.

One-Pot Synthesis of Chloromethylated Mesoporous Silica Nanoparticles as Multifunctional Fillers in Hybrid Anion Exchange Membranes

Chloromethylated mesoporous silica nanoparticles （CM MSN） were synthesized through co-condensation of tetraethoxysilane and （chloro） phenyltrimethoxysilane precursors using hexadecyl trimethyl ammonium bromide as template.With the addition of the particles into chloromethylated poly （ether ether ketone） （PEEK）,the hybrid membranes were prepared by a solution-casting method after complete quatemization of the casting solution.The successful synthesis of the particles was verified by transmission electron microscopy,X-ray diffraction and Fourier transform infrared spectroscopy while the effect of CM MSN incorporation on membrane performance including thermal stability,mechanical strength and hydroxide conductivity was investigated by thermal gravimetric analysis,electronic stretching machine,alternating-current impedance and so on.Owing to the large pore volume and high surface area of the particles,the hybrid membranes exhibited enhanced hydroxide conductivity （88.7% increase at 60 ℃,100% RH with 5.0 wt% filling content） due to an increase in ion concentration and optimization of the channel morphology.Besides,higher mechanical strength,thermal and dimensional stability of hybrid membranes were obtained compared with those of the imidazolium PEEK membrane.

Preparation of Anion Exchange Membrane Based on Imidazolium Functionalized Poly（arylene ether ketone）

The authors presented a novel synthetic route for the imidazolium functionalized poly（arylene ether ke- tone）s, derived from an engineering plastics polymer, a poly（arylene ether ketone） with 3,3＇,5,5＇- tetramethyl-4,4＇-dihydroxybiphenyl moiety（PAEK-TM）. The preparation of anion exchange membranes comprised converting benzylic methyl groups to bromomethyl groups by a radical reaction, followed by the functionalization of bromomethylated PAEK with alkyl imidazoles, i.e., methyl, butyl or vinyl imidazole. The structure of imidazolium functionalized PAEK was proved by 1H NMR spectra. A class of flexible and tough membranes was then achieved by subsequent film-forming and anion exchange processes. The water uptake and hydroxide conductivities of mem- branes are comparable or superior to those of quaternary ammonium（QA） anion exchange membranes. This work demonstrated a new route for non-QA anion exchange membrane design, avoiding the chloromethylation reagent and oreciselv controlling the degree and location of imidazolium grouos.