Search

A series of sulfonated poly(arylene ether sulfone) block copolymers with aliphatic chains (SPAES-LA) to lend structural flexibility in the polymer backbone have been synthesized to prepare proton exchange membranes (PEMs) showing improved electrochemical performance and dimensional/oxidative stabilities. The SPAES-LAs, bearing different hydrophilic/hydrophobic segment lengths, are prepared via polycondensation and sulfonation reactions. The sulfonation reaction occurs in specific fluorenylidene units by using chlorosulfonic acid. The SPAES-LA membrane, fabricated by solvent casting method, exhibits remarkable dimensional/thermal stabilities. Moreover, proton conductivity of as-prepared SPAES-LA membranes demonstrates significant improvement with expansion of ion clusters which is due to the increased hydrophilic volume ratio. In particular, the SPAES-LA-X12Y28 membrane exhibited heightened proton conductivity of 158.4 mS cm−1 as well as suitable dimensional stability and durability towards radical oxidation, due to an effective well-defined hydrophilic-hydrophobic interface. Furthermore, H 2 /O 2 fuel cell performance using SPAES-LA-X12Y28 membrane achieves a maximum power density of 232.02 mW cm−2, a result which points out that SPAES-LA membranes show great potential for applications of polymer electrolyte membrane. Image 1 • The block copolymers are synthesized via controlling oligomer lengths. • The fabricated membranes show desirable thermo-oxidative stability. • The membranes showed high physio-chemical properties. • The as-prepared membranes exhibit high ionic conductivity and unit-cell performance. [ABSTRACT FROM AUTHOR]

Abstract A series of composite membranes for application as anion exchange membranes were prepared by introducing various amounts (0.1–5.0 wt%) of reduced graphene oxide (rGO) into chloromethylated poly(arylene ether ketone) (CM-PAEK), followed by quarternization and anionization. CM-PAEK/rGO composite membranes with controlled weight ratios of rGO were fabricated by cost-competitive solution casting method. The field emission scanning electron microscopy (FE-SEM) images of the composite membranes showed that the distribution of rGO was uniform, and the prepared membranes have similar thicknesses confirmed by the cross-sectional image. The composite membranes exhibited enhanced the mechanical strength due to π-π interaction between the aromatic chain of rGO and the polymer backbone, and after the quaternization, hydroxide conduction was improved by hydrogen bonding between rGO and functional ammonium groups. Among the QN-PAEK/rGO membranes with various amounts of rGO, QN-PAEK/rGO 1.0 wt% demonstrated the highest ionic conductivity of 115 mS cm−1, and other composite membranes, which were blended more than that (3 wt% and 5 wt%), showed a decrease in ionic conductivity due to aggregation of inorganic nano fillers. Furthermore, alkaline resistance, mechanical strength, and dimensional stability of composite membranes have been greatly improved due to the introduction of rGO, which demonstrate great potential application as anion exchange membrane for fuel cells. Graphical abstract Image 1 Highlights • QN-PAEK/rGO composite membranes were prepared by introducing various amount of rGO. • The QN-PAEK/rGO composite membranes demonstrated superior OH− conductivity. • The prepared membranes showed improved mechanical and dimensional stabilities. • The membranes exhibited remarkable alkaline stability in a 2 M NaOH solution for 600 h. [ABSTRACT FROM AUTHOR]

A new series of partially fluorinated and sulfonated poly(biphenylsulfone ketone) block copolymers as proton exchange membrane materials were prepared from hydrophilic and hydrophobic oligomers. The copolymers were characterized by proton NMR, FT-IR, GPC, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) thermograms. The membranes showed excellent thermal and oxidative stability; e.g., TGA and DSC demonstrated that all sulfonated block copolymers exhibited good thermal stability with an initial weight loss at temperatures above 200 °C. Block-30 membranes showed low water uptake and acceptable ionic exchange capacity (IEC). The proton conductivity of the block-30 was 75 mS cm−1 at 90 °C and 100% relative humidity (RH), while Nafion-117 had a value of 98 mS cm−1 under the same conditions. AFM analysis of the Block-30 clearly showed that the morphology of the membranes separated the hydrophilic and hydrophobic domains which provided an effective proton-transport pathway. [ABSTRACT FROM AUTHOR]

Novel anion conductive nanocomposite membranes with superb hydroxide conductivity and chemical durability in alkaline conditions were prepared by the introduction of quaternary ammonium functionalized graphene oxide (Q-GO) into quaternized poly(arylene ether) (QPAE) random copolymer. Q-GO containing amino silane units, which induce ion cluster formation in the polymer matrix, was synthesized using (3-aminopropyl)triethoxysilane (APTS) and (3-bromopropyl)trimethyl ammonium bromide (PTMA) as the main quaternization reagents. The chemical structures and morphologies of the polymers and inorganic nanofillers were characterized by 1H NMR, FT-IR, FE-SEM, XPS, and SAXS. GO-(APTS- c -PTMA), the so called Q-GO, was used to expand the ion transfer sites and improve the physicochemical stability of the membrane. The electrochemical properties, thermal/mechanical properties, and chemical stabilities of the anion exchange membranes (AEMs) were investigated in accordance with different contents of GO-(APTS- c -PTMA). The π-π bonds between the polymer matrix and the Q-GO resulted in improved dimensional stability and mechanical properties in the composite membrane. The QPAE/GO-(APTS- c -PTMA) 0.7 wt% membrane showed the highest hydroxide conductivity of 114.2 mS cm−1 at 90 °C with an ion exchange capacity of 1.45 mmol g−1, which is 2.07 times higher than the pristine membrane (55.1 mS cm−1 at 90 °C). Furthermore, the single-cell performance of the QPAE/GO-(APTS- c -PTMA) 0.7 wt% as an AEM showed an excellent maximum power density of 135.8 mW cm−2 at 70 °C. Image 1 • Cheap and easy method for crosslinked anion exchange membrane (AEM) preparation for anion exchange membrane fuel cells AEMFC. • The composite AEMs showed highest hydroxide conductivity. • The prepared composite AEMs exhibit long-term chemical stability (>20 days). • The cell was stably operated at 60 °C for 120 h. [ABSTRACT FROM AUTHOR]

In this study, quaternized poly (arylene ether sulfone) (QNPAES) was synthesized using conventional nucleophilic aromatic polycondensation. We then developed a blended membrane composed of sulfonated poly (ether ether ketone) (SPEEK) using facile solution casting. A series of mixed hybrid membranes of SPEEK/QNPAES were prepared by varying the wt% of QNPAES mixed with SPEEK. The results showed that an appropriate amount of QNPAES (i.e., 6 wt%) could significantly improve the mechanical strength, proton conductivity and physicochemical properties of a prepared mixed membrane, as well as the proton exchange membrane fuel cell (PEMFC) performance and durability at relative humidity (RH) of 20%. Specifically, a SPEEK/QNPAES at 6 wt% provides a current output, power output and endurance of 0.431 A cm−2, 0.15 W cm−2 and over 900 h, respectively, at an RH of 20% and 60 °C. These results can be attributed to acid-base ionic crosslinking, which offers effective interfacial compatibility between SPEEK and QNPAES. A PEMFC with SPEEK/QNPAES membranes when used at 20% RH achieved significantly advanced performance and ultra-high, long-term durability compared with those of PEMFCs with bare SPEEK, suggesting that SPEEK/QNPAES membranes can be used as polymer electrolyte membranes. Proton transport of SPEEK/QNPAES acid-base blended membranes for PEFC performance and ultra-high, long-term durability over 900 h. [Display omitted] • QNPAES was synthesized using conventional nucleophilic aromatic polycondensation. • The SPEEK/QNPAES (6 wt%) demonstrated significantly improved proton conductivity. • Acid-base crosslinking offers effective compatibility between SPEEK/QNPAES. • The SPEEK/QNPAES provides maximum current output and power density. • The SPEEK/QNPAES exhibits long-term durability under 20% RH for 900 h. [ABSTRACT FROM AUTHOR]

We present a volumetric interferometer that has been specially designed to improve the measurement accuracy of the three-dimensional coordinate metrology by reducing excessive Abbe offsets. The interferometer is composed of two main parts; one is a three-dimensionally movable target and the other is a stationary two-dimensional array of photo-detectors. The target made of point diffraction sources emanates two spherical wavefronts, of which interference intensity is monitored by the photo-detectors. Applying phase shifting allows the phases of the photo-detectors to be precisely obtained, and the measured phases are fitted to a geometric model of multilateration so as to determine the xyz-location of the target by minimizing least square errors. A prototype built on a CMM demonstrates that the proposed interferometer is capable of measuring the xyz-coordinates of the probe with a volumetric uncertainty of less than 1.0 μm. [Copyright &y& Elsevier]