Rubbery polymer membranes prepared from CO2-philic PEO and/or highly permeable PDMS are desired for efficient CO2 separation from light gases (CH4 and N2). Poor mechanical properties and size-sieving ability, however, limit their application in gas separation applications. Cross-linked rubbery polymer-based gas separation membranes with a low Tg based on both PEG/PPG and PDMS units with various compositions between these two units are prepared for the first time in this work by ring-opening metathesis polymerization type cross-linking and in situ membrane casting. The developed membranes display excellent CO2 separation performance with CO2 permeability ranging from 301 to 561 Barrer with excellent CO2/N2 selectivity ranging from 50 to 59, overcoming the Robeson upper bound (2008). The key finding underlying the excellent performance of the newly developed cross-linked x(PEG/PPG:PDMS) membranes is the formation of a well-connected interlocked network structure, which endows the rubbery materials with the properties of rigid polymers, e.g., size-sieving ability and high thermomechanical stability. Moreover, the membrane shows long-term antiaging performance of up to eight months and antiplasticization behavior up to 25 atm pressure.
Anion exchange membrane fuel cells (AEMFCs) have drawn growing interests in the past decade.The inexpensive non-platinum group metal (non-PGM) catalyst and faster oxygen reduction reactions (ORRs) kinetic at high pH are the potential driving force to develop AEM materials.Despite numerous studies, molecular design rules have not yet been fully elucidated for the development of highly conductive and alkaline stable AEMs. Polymer materials that can produce tunable nanoscale and well-developed micro-phase separated morphology hold great promises as highly conductive and alkaline stable AEMs.Understanding the relationship between the structure and electrical/physicochemical properties of the corresponding AEMs are critical to the rational design and development of AEMs. We report herein a systematic approach to develop highly conductive and alkaline stable anion exchange membranes based on the non-(aryl ether) polymer backbone grafted with the pendant quaternary ammonium as an ion-conducting head group and the alkyl chain as a hydrophobic spacer in different ways. The effects of structure on the properties of the corresponding AEMs such as morphology, ion conductivity, physicochemical properties, and fuel cell properties will be investigated in detail.
Poly(2,6-dimethyl-1,4-phenylene oxide)s (PPOs)-based anion exchange membranes (AEMs) with four of the most widely investigated head groups were prepared. Through a combination of experimental and simulation approaches, the effects of the different types of head groups on the properties of the AEMs, including hydroxide conductivity, water content, physicochemical stability, and fuel cell device performance were fully explored. Unlike other studies, in which the conductivity was mostly investigated in liquid water, the conductivity of the PPO-based AEMs in 95% relative humidity (RH) conditions as well as in liquid water was investigated. The conductivity trend in 95% RH condition was different from that in liquid water but corresponded well with the actual cell performance trend observed, suggesting that the AEM fuel cell performance under in situ cell conditions (95% RH, 60 °C, H2/O2) is more closely related to the conductivity measured ex situ under 95% RH conditions (60 °C) than in liquid water. On the basis of the conductivity data and molecular simulation results, it was concluded that the predominant hydroxide ion-conducting mechanism in liquid water differs from that in the operating fuel cell environment, where the ionomers become hydrated only as a result of water vapor transported into the cells.
We report semi-interpenetrating polymer network (semi-IPN) membranes prepared easily from a cross-linked network using poly(acrylic acid) (PAA) and poly(vinyl alcohol) (PVA) with interpenetrated Nafion for both proton-exchange membrane fuel cell (PEMFC) and proton-exchange membrane water electrolyzer (PEMWE) applications. Thermal esterification between PAA and PVA induced three-dimensional cross-linking to improve mechanical toughness and reduce hydrogen crossover, while the hydrophilic nature of the PAA–PVA-based cross-linked matrix still enhanced the water uptake (WU) and hence conductivity of the Nafion penetrant. The semi-IPN membrane (NPP-95) composed of Nafion, PAA, and PVA with a ratio of 95:2.5:2.5 showed a hexagonal cylindrical morphology and improved thermal, mechanical, and dimensional stability compared to a recast Nafion membrane (re-Nafion). The membrane was also highly effective at managing water due to its low WU and high conductivity. Furthermore, its hydrogen permeability was 49.6% lower than that of re-Nafion under the actual fuel cell operating conditions (at 100% RH and 80 °C). NPP-95 exhibited significantly improved conductivity and PEMFC performance compared to re-Nafion with a current density of 1561 mA/cm2 at a potential of 0.6 V and a peak power density of 1179 mW/cm2. Furthermore, in the PEMWE performances, NPP-95 displayed about a 1.5-fold higher current density of 4310 mA/cm2 at 2.0 V and much lower ohmic resistance than re-Nafion between 60 and 80 °C.
Abstract An environmentally friendly, four‐component, one‐pot condensation reaction of phthalimide or phthalic anhydride, various aromatic aldehydes, ethylcyanoacetate, and hydrazine hydrate is presented.
An efficient, four-component, one-pot condensation reaction of phthalimide or phthalic anhydride, aromatic aldehydes, and ethyl cyanoacetate for the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-dione derivatives mediated by L-proline in excellent yields is reported.
Nafion, as a perfluorosulfonic acid (PFSA)-based polymer, is a key material that contributes to the commercialization of proton exchange membrane fuel cells (PEMFCs). The high dependence on relative humidity (RH) of Nafion or other PFSA membranes for proton conduction, together with its decreased mechanical and dimensional stability and high fuel (H2) crossover at the cell operating temperatures (80 °C or above), however, remain issues that have yet to be solved. In the current work, thin sulfonated poly(arylene ether sulfone) (sPES)-coated Nafion membranes (sPES-c-Nafions) are developed, for the first time, by simply spin-coating the sPES solution onto a Nafion membrane, and the results are compared with the sPES-blended Nafion counterparts. The sPES-c1-Nafion demonstrates a very high proton conductivity of 223.3 mS cm–1 (80 °C) and a very low hydrogen permeability, a 41% reduction compared to that of Nafion-212, together with improved mechanical and dimensional stabilities compared to Nafion-212. The developed membrane also shows excellent cell performance (i.e., with a current density of 1.56 A cm–2 and a peak power density of 1.20 W cm–2 at 0.6 V potential in the actual operating conditions of PEMFCs).
Random copolymers made of both (PIM-polyimide) and (6FDA-durene-PI) were prepared for the first time by a facile one-step polycondensation reaction. By combining the highly porous and contorted structure of PIM (polymers with intrinsic microporosity) and high thermomechanical properties of PI (polyimide), the membranes obtained from these random copolymers [(PIM-PI)x-(6FDA-durene-PI)y] showed high CO2 permeability (> 1047 Barrer) with moderate CO2/N2 (> 16.5) and CO2/CH4 (> 18) selectivity, together with excellent thermal and mechanical properties. The membranes prepared from three different compositions of two comonomers (1:4, 1:6 and 1:10 of x:y), all showed similar morphological and physical properties, and gas separation performance, indicating ease of synthesis and practicability for large-scale production. The gas separation performance of these membranes at various pressure ranges (100–1500 torr) was also investigated.
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