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A novel polymer polysulfone (PSF)-graft-4′-aminobenzo-15-crown-5-ether (AB15C5) (PSF-g-AB15C5) for lithium isotope separation was prepared from PSF and AB15C5 as starting materials via nucleophilic substitution reaction. The chemical structure and properties of PSF-g-AB15C5 polymers were characterized by FT-IR, 1 H NMR, XPS, and TGA. The polymers obtained were used for lithium isotope separation by solid−liquid extraction. The effects of the immobilization amount of crown ether grafting on PSF, the type of counteranion of lithium salt, and the kind of solvent on the single stage separation factor were explored. Results showed that the single stage separation factor was only 1.002 ± 0.002 for AB15C5 in the traditional liquid−liquid extraction system of H 2 O−LiCl/CHCl 3 −AB15C5, whereas the single stage separation factor increased from 1.003 ± 0.001 to 1.015 ± 0.002 with the increase of the immobilization amount of crown ether from 0.23 to 0.79 mmol g −1 on PSF-g-AB15C5 polymers in the solid−liquid extraction system of CH 3 OH−LiCl/PSF-g-AB15C5 polymers. The order of the single stage separation factor obtained in different lithium salts was LiI > LiBr > LiClO 4 > LiCl. Further, the maximum value of single stage separation factor was 1.031 ± 0.002 for the extraction system of CH 3 NO 2 −LiCl/PSF-g-AB15C5 polymers. Moreover, 6 Li and 7 Li were enriched in the polymer phase and the solution phase, respectively.

High proton conductivity and sufficient stability of the polybenzimidazole membrane are important for the application of high-temperature proton exchange membrane fuel cells (HT-PEMFCs). A series of composite membranes based on crosslinked mPBI (cPBI) with cerium 2,4,6-triphosphono-1,3,5-triazine (CeTPT) were resoundingly fabricated. Novel cPBI networks with tetrafunctional N,N,N′,N′-tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) were synthesized. It is noteworthy that a new high-temperature proton conductor CeTPT was added. CeTPT contained three phosphonic acid groups, which offered good proton conductivity at moderate-to-low humidity and had good thermal stability. Tetrafunctional crosslinker TGDDM had multiple functional groups. With a relatively low crosslinking degree (CLD), the mechanical properties, dimensional stability, and oxidative resistance of the membranes were efficiently improved. The low CLD and good physicochemical stability also allowed high doping levels of CeTPT (up to 50%) and consequently high proton conductivity. At 180 °C and 50% RH, the proton conductivity of cPBI-5-CeTPT-50 and cPBI-10-CeTPT-50 was 0.072 and 0.068 S cm–1, respectively. The cPBI-CeTPT membranes showed good methanol resistance and membrane selectivity, and thus the membranes were suitable for direct methanol fuel cells.

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An insoluble sulfonated polyphosphazene (SPOP) with high degree of sulfonation is synthesized and used as the proton conductor in polybenzimidazole (PBI) high-temperature proton exchange membrane. Polyfunctional triglycidyl isocyanurate (TGIC) is used as covalent cross-linking agent to obtain a high proton conductivity at low cross-linking degrees. The composite membrane is characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscope (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD). SPOP has good compatibility with mPBI-TGIC, leading to uniform dispersion in the obtained membranes with neither phase separation nor agglomeration. As a highly efficient cross-linking agent, TGIC not only makes the composite membrane have good mechanical properties, thermal stability, anti-swelling and anti-oxidation properties at low crosslinking degrees, but also leads to high doping amount of SPOP, thus making the composite the membrane have a high proton conductivity. The conductivity of mPBI-TGIC(5%)/SPOP(50%) at 100% RH, 50% RH and 0 RH is 0.143, 0.076 and 0.044 S cm −1 at 180 °C, respectively. In addition, the composite membranes has good methanol resistance and selectivity, so the composite membrane can be applied in the direct methanol fuel cell.