Arylene

Abstract: Good salt rejection and flux characteristics can be obtained with reverse osmosis membranes made from crosslinked, interfacially polymerized aromatic polyamides, particularly poly(arylenepolyamine aromaticpolycarboxylamides) such as poly(phenylenediamine trimesamide). The aromatic polyamides are preferably synthesized directly from an essentially monomeric polyacyl halide (at least tri- or higher in acyl functionality) and an essentially monomeric arylene polyamine with a measurable water solubility. As compared to closely analogous linear polymers, these interfacially polymerized, crosslinked polyamides have a lower % elongation and lower solubility (e.g. in amide solvents). Chlorine resistance characteristics of these polyamides are also good and can be improved by treatment with a chlorinating agent. In the preferred practice of the method for making a reverse osmosis membrane, a porous support layer is coated with the polyamine component (e.g. an aqueous solution of phenylene diamine); the thus-coated support is contacted with the polyacyl halide component (e.g. trimesoyl chloride), thereby initiating the interfacial polymerization in situ on the support; and the resulting product is dried to provide a composite membrane comprising the polyamide laminated to the porous support.

Abstract: Anion conductive aromatic multiblock copolymers, poly(arylene ether)s containing quaternized ammonio-substituted fluorene groups, were synthesized via block copolycondensation of fluorene-containing (later hydrophilic) oligomers and linear hydrophobic oligomers, chloromethylation, quaternization, and ion-exchange reactions. The ammonio groups were selectively introduced onto the fluorene-containing units. The quaternized multiblock copolymers (QPEs) produced ductile, transparent membranes. A well-controlled multiblock structure was responsible for the developed hydrophobic/hydrophilic phase separation and interconnected ion transporting pathway, as confirmed by scanning transmission electron microscopic (STEM) observation. The ionomer membranes showed considerably higher hydroxide ion conductivities, up to 144 mS/cm at 80 °C, than those of existing anion conductive ionomer membranes. The durabilities of the QPE membranes were evaluated under severe, accelerated-aging conditions, and minor degradation was ...

Abstract: A series of poly(arylene piperidinium)s (PAPipQs) devoid of any alkali-sensitive aryl ether bonds or benzylic sites are prepared and studied as anion exchange membranes (AEMs) for alkaline fuel cells. First, the excellent alkaline stability of the model compound 4,4-diarylpiperidinium is confirmed. Medium molecular weight poly(arylene piperidine)s are then synthesized in polycondensations of N-methyl-4-piperidone and either bi- or terphenyl via superelectrophilic activation in triflic acid. Film-forming PAPipQs are subsequently prepared in Menshutkin reactions with methyl, butyl, hexyl, and octyl halides, respectively. AEMs based on poly(terphenyl dimethylpiperidinium) show the best performance with no structural degradation detectable by 1H NMR spectroscopy after storage in 2 maq. NaOH at 60 °C after 15 d, and a mere 5% ionic loss at 90 °C. In the fully hydrated state these AEMs reach an OH− conductivity of 89 mS cm−1 at 80 °C. The presence of longer pendant N-alkyl chains (butyl to octyl) is found to significantly promote Hofmann ring-opening elimination reactions and the degradation rate increases with increasing alkyl chain length. The results of the present study demonstrate that PAPipQs are efficiently prepared from readily available monomers and show excellent alkaline stability and OH− conductivity when devoid of pendant N-alkyl chains. (Less)