Proton-conducting superacidic polymer membranes with different fluoroalkyl sulfonate pendants attached to aromatic polymer backbones were synthesized via C−H functionalization and Suzuki coupling reactions. Variation in the chemical structures of the pendant acidic sulfonate moieties and their effects on membrane properties including water uptake, ion exchange capacity, morphology, and proton conductivity were systemically investigated. Membranes containing the short −OCF 2 SO 3 H pendant (PSU-S 5 ) showed a smaller hydrophilic domain size and lower proton conductivity than those containing the longer pendants −OCF 2 CF 2 SO 3 H (PSU-S 1 ) and −SCF 2 CF 2 SO 3 H (PSU-S 4 ), likely due to the short chain's less favorable aggregation and lower acidity. Polymer electrolyte membranes with unique branched fluoroalkyl sulfonate pendants (PSU-S 6 ) gave larger ionic domain sizes, more uniform hydrophilic channels, and higher proton conductivity than samples with analogous linear pendant chains (PSU-S 1 ), indicating that branched sulfonate structures may be a key future direction in the field of fuel cell membrane. ■ INTRODUCTIONIncreasing concerns about the environmental impact of our overdependence on fossil fuels have motivated research on alternative clean energy technologies. Proton exchange membrane (PEM) fuel cells, which are composed of a cathode, an anode, and a PEM, generate electricity cleanly via electrochemical reactions of hydrogen and oxygen to yield water and heat as the only byproducts. 1−5 The development of perfluorosulfonic acid ionomers, such as Nafion, has greatly contributed to fuel cell technologies, and these materials are still widely used as the benchmark membrane in fuel cells. Because of its perfluorinated structure and superacidic pendant side chain, Nafion possesses high proton conductivity as well as good chemical stability. However, Nafion is still not an ideal PEM material, and its drawbacks (e.g., high cost, low operation temperature, and high methanol crossover) require development of alternative PEMs for successful adoption of fuel cells as reliable and inexpensive energy conversion devices. 6−9 Over the past decades, extensive efforts have been devoted to the development of hydrocarbon-based PEMs, and many aryl and alkyl sulfonated polymers have been described. 10−16 In general, these sulfonated aromatic polymer PEMs with high ion exchange capacity and high conductivity swell excessively under high hydration conditions and give much lower proton conductivity than Nafion when the relative humidity (RH) or water content of the membrane is reduced. PEMs with good proton conductivity at high temperature (above 100°C) and low RH can bring many advantages to the fuel cell system, such as fast electrode reaction kinetics, good tolerance toward carbon monoxide and other fuel and air impurities, and simplified water management strategies. 8,13,17−19 To achieve highly conductive materials under low hydration conditions, creation of well-connected hydrophilic channels within the membrane throu...

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Microporous materials have the potential to enable new low energy separation processes due to their superb textural properties and structural diversity, yet these materials are facing practical challenges in large-scale applications. Opportunities for advancing microporous sorbents lie in a technology that can bridge the gap between high-performance materials and scalable separation devices. This perspective article discusses the current state of the art and the potential of the fiber sorbent-based separation processes by highlighting the structure–property–performance relationships, candidate porous materials, and application areas.

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Oltipraz, a cancer chemopreventive agent, has antitumor and antiangiogenic effects. In animal models and clinical studies, a considerable amount of oltipraz is metabolized to pyrrolopyrazines, including M2, 7-methyl-6,8-bis(methylthio)pyrrolo[1,2-a]pyrazine; M3, 7-methyl-8-(methylsulfinyl)-6-(methylthio)pyrrolo[1,2-a]pyrazine and M4, 7-methyl-6,8-bis(methylsulfinyl)pyrrolo[1,2-a]pyrazine. In view of the role of hypoxia-inducible factor-1 (HIF-1) α in tumor growth and angiogenesis, this study investigated whether pyrrolopyrazine metabolites of oltipraz inhibit HIF-1α induction, and if so, what the molecular basis is. M2 treatment inhibited the induction of HIF-1α by a variety of stimuli including insulin, hypoxia, CoCl(2) and hydrogen peroxide in HCT116 cells, whereas M3 or M4 failed to do so. Consistently, M2 prevented HIF-1α target gene induction. Moreover, it inhibited cancer cell invasion and migration. M2 caused no change in the expression of HIF-1α transcript but increased the levels of precursor forms of microRNAs (miRNAs) 199a-5p and 20a, but not those of primary forms, indicating facilitation of the maturation process of the miRNAs by M2. Increased levels of the miRNAs contributed to HIF-1α repression, as shown by the results of experiments using mimics. Consistently, M2 treatment inhibited de novo synthesis of HIF-1α, as supported by decreased incorporation of [(35)S]-methionine into HIF-1α with no changes in its ubiquitination or degradation. 7-Ethyl-6,8-bis(methylthio)pyrrolo[1,2-a]pyrazine, a synthetic analog of M2, had a similar inhibitory effect. In conclusion, M2 with pyrrolopyrazine structure and its 7-ethyl congenor have the ability to prevent the induction of HIF-1α, which may result from the inhibition of HIF-1α de novo synthesis, as mediated by the induction of miR-199a-5p and miR-20a.