Vinyl functionalized hollow silica spheres (HSSs) were prepared via a template method and surface modification thereafter. Poly(vinylbenzyl phosphonic acid) (PVBPA) grafted HSSs (HPSSs) were prepared via emulsion polymerization of diisopropyl p-vinylbenzyl phosphonate (DIPVBP) on the surface of HSSs, and hydrolysis thereafter. The chemical structure and morphology of HPSSs were characterized by FTIR and TEM. A series of proton exchange membranes based-on Nafion ® 212 and HPSSs were prepared via solution casting . The water uptake, swelling ratio, mechanical properties , thermal behavior, proton conductivity , and chemical oxidative stability of the composite membranes were investigated. The addition of HPSSs in Nafion ® membranes can improve the water retentivity of the composite membranes. The composite membranes with HPSSs exhibit higher water uptake and proton conductivity than that of the recast Nafion ® membranes. The water uptake and the proton conductivity of the composite membranes increase with increasing HPSSs loading. With the higher water retentivity, the membranes exhibit high proton conductivity at high temperature (1.6 × 10 −1 S cm −1 at 125 °C).
Polyhedral oligomeric silsesquioxane (POSS) has attracted increasing attention because of its organic/inorganic, nanosize, easily functional nature, especially in the applications of direct methanol fuel cells (DMFCs). In this work, we have successfully synthesized a novel bifunctional POSS ( Vi -POSS-SO 3 Na) with vinyl and sulfonic acid groups by thiol-ene click reaction. Vi -POSS-SO 3 Na was introduced into Nafion® matrix and cross-linked by in-situ simply thermal treatment. The implantation of the bifunctional POSS filler gives significant improvements in the performance of such proton exchange membranes (PEMs). The cross-linked hybrid membrane with 12 wt% of Vi -POSS-SO 3 Na ( X -Nafion@POSS-12) has a high proton conductivity (121 mS cm −1 ) at 80 °C, excellent dimensional stability and the lowest methanol permeability (5.4 × 10 −8 cm 2 s −1 ). The highest power density of the DMFCs was obtained by using the X -Nafion@POSS-12 as PEM in DMFC at 80 °C, and its value (34.93 mW cm −2 ) is twice higher than that of Nafion 212 membrane (14.90 mW cm −2 ). The novel in-situ fabrication method gives a simple and potential approach for the preparation of PEMs used in DMFCs.
Amphiphobic fluorine materials hold great promise for fabricating self-cleaning membranes. However, the severely impeded water transport in hydrophobic fluorine-based membranes and the weak interaction with the substrate of the low-surface-energy fluorine materials represent two major obstacles for efficient water purification. Herein, we design an ultrathin fluorine-based membrane via coordination-driven metal-bridging assembly. An Fe3+-rich metal–organic layer is constructed on a porous substrate by coordination between polyphosphate ligands and Fe3+ ions, accompanied by the assembly of perfluorosulfonate polymer ligands (Nafion®) via the bridging effect of Fe3+ ions for the metal-bridging fluorine-based membrane (MBFM). By virtue of the flexible modulation of Fe3+ and unique self-assembly of Nafion®, a defect-free 58 nm-thick MBFM featuring an ultrahigh surface fluorine content (47.6 at%) and underwater superoleophobicity (∼160°) is achieved, which displays a superior water permeance of 125.2 L m−2 h−1 bar−1 (2–10 times higher than that of state-of-the-art membranes with dye rejections above 90%) and versatile resistance towards both spreading and non-spreading foulants (flux decline ratios below 8%). This metal-bridging assembly strategy may shed light on advanced membrane fabrication from rationally designed ligands and functional moieties.
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