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Jiandang Xue - One of the best experts on this subject based on the ideXlab platform.

  • uv crosslinking of polystyrene anion exchange membranes by azidated macromolecular Crosslinker for alkaline fuel cells
    Journal of Membrane Science, 2017
    Co-Authors: Jiandang Xue, Lei Liu, Jiayou Liao, Yinghua Shen
    Abstract:

    Abstract Poly(2,6-dimethyl-phenyleneoxide)s (PPO)s with photo-crosslinkable azide groups were employed as macromolecular Crosslinker for poly(vinylbenzyl chloride) (PVBC)-based anion exchange membranes (AEMs). The crosslinked AEMs were achieved by solution casting and UV- irradiation, subsequently quaternization with trimethylamine. Although the presence of azide groups in IR spectra in crosslinked AEMs suggested the incomplete reaction of azide groups using UV-irradiation, the gel fractions were more than 85% indicating the successful crosslinking between PVBC and PPO macromolecular Crosslinker. The key properties of the crosslinked AEMs, such as mechanical property, ion exchange capacity, thermal stability, water uptake, ion conductivity, alkaline stability and initial H 2 /O 2 fuel cell performance were investigated. Excellent mechanical properties were observed for all of the crosslinked AEMs. The as-obtained AEMs showed comparable λ-normalized hydroxide conductivity with previous reported crosslinked AEMs. The highest hydroxide conductivity of 14.8 mS/cm at 20 °C was achieved for the crosslinked AEMs with IEC value of 1.95 meq./g in spite of its low water uptake (19.8 wt%). Moreover, excellent alkaline stability was observed for crosslinked AEMs, 15% decrease in hydroxide conductivity after alkaline stability testing 1 M NaOH at 80 °C for 500 h, while the conductivity of uncrosslinked membrane with similar IEC value decreased sharply with 58% of conductivity loss after only 120 h. The improved alkaline stability of the crosslinked AEMs may be derived from its compact crosslinked architecture, protecting the cations from severe degradation. A peak power density of 11 mW/cm 2 was obtained at 16 mA/cm 2 when the crosslinked AEM was used as polymer electrolyte membrane in H 2 /O 2 alkaline fuel cell at 60 °C.

Yun Zhao - One of the best experts on this subject based on the ideXlab platform.

  • crosslinked poly vinylbenzyl chloride with a macromolecular Crosslinker for anion exchange membrane fuel cells
    Journal of Power Sources, 2014
    Co-Authors: Zhigang Shao, Geng Zhang, Yun Zhao
    Abstract:

    Abstract A new material based on crosslinked poly(vinylbenzyl chloride) (PVBC) with a macromolecular Crosslinker is synthesized and employed as the membrane for anion exchange membrane fuel cells (AEMFCs). PVBC is used as the hydroxide conducting polymers, while poly(vinyl acetal) (PVAc) containing dimethylamino groups plays the role as macromolecular Crosslinker and the supporting matrix simultaneously. Fourier transform infrared (FT-IR) absorption spectra and X-ray photoelectron (XPS) spectra prove successful crosslinking between PVBC and PVAc. The crosslinked membrane shows hydroxide conductivity larger than 0.01 S cm−1 at room temperature, and the swelling by water at elevated temperature is suppressed. The H2/O2 AEMFC using the crosslinked membrane shows a peak power density (Pmax) of 124.7 mW cm−2 at 40 °C, and the decrease of the open circuit voltage (OCV) of the fuel cell is negligible under continuous OCV conditions for 120 h. All the results indicate that the crosslinking with a macromolecular Crosslinker may be a promising strategy to fabricate anion exchange membrane for the application in the AEMFCs.

Geng Zhang - One of the best experts on this subject based on the ideXlab platform.

  • crosslinked poly vinylbenzyl chloride with a macromolecular Crosslinker for anion exchange membrane fuel cells
    Journal of Power Sources, 2014
    Co-Authors: Zhigang Shao, Geng Zhang, Yun Zhao
    Abstract:

    Abstract A new material based on crosslinked poly(vinylbenzyl chloride) (PVBC) with a macromolecular Crosslinker is synthesized and employed as the membrane for anion exchange membrane fuel cells (AEMFCs). PVBC is used as the hydroxide conducting polymers, while poly(vinyl acetal) (PVAc) containing dimethylamino groups plays the role as macromolecular Crosslinker and the supporting matrix simultaneously. Fourier transform infrared (FT-IR) absorption spectra and X-ray photoelectron (XPS) spectra prove successful crosslinking between PVBC and PVAc. The crosslinked membrane shows hydroxide conductivity larger than 0.01 S cm−1 at room temperature, and the swelling by water at elevated temperature is suppressed. The H2/O2 AEMFC using the crosslinked membrane shows a peak power density (Pmax) of 124.7 mW cm−2 at 40 °C, and the decrease of the open circuit voltage (OCV) of the fuel cell is negligible under continuous OCV conditions for 120 h. All the results indicate that the crosslinking with a macromolecular Crosslinker may be a promising strategy to fabricate anion exchange membrane for the application in the AEMFCs.

Pablo A Iglesias - One of the best experts on this subject based on the ideXlab platform.

  • interactions between myosin and actin Crosslinkers control cytokinesis contractility dynamics and mechanics
    Current Biology, 2008
    Co-Authors: Elizabeth M Reichl, Yixin Ren, Mary K Morphew, Michael Delannoy, Janet C Effler, Kristine D Girard, Srikanth N Divi, Pablo A Iglesias
    Abstract:

    Summary Introduction Contractile networks are fundamental to many cellular functions, particularly cytokinesis and cell motility. Contractile networks depend on myosin-II mechanochemistry to generate sliding force on the actin polymers. However, to be contractile, the networks must also be crosslinked by crosslinking proteins, and to change the shape of the cell, the network must be linked to the plasma membrane. Discerning how this integrated network operates is essential for understanding cytokinesis contractility and shape control. Here, we analyzed the cytoskeletal network that drives furrow ingression in Dictyostelium . Results We establish that the actin polymers are assembled into a meshwork and that myosin-II does not assemble into a discrete ring in the Dictyostelium cleavage furrow of adherent cells. We show that myosin-II generates regional mechanics by increasing cleavage furrow stiffness and slows furrow ingression during late cytokinesis as compared to myoII nulls. Actin Crosslinkers dynacortin and fimbrin similarly slow furrow ingression and contribute to cell mechanics in a myosin-II-dependent manner. By using FRAP, we show that the actin Crosslinkers have slower kinetics in the cleavage furrow cortex than in the pole, that their kinetics differ between wild-type and myoII null cells, and that the protein dynamics of each Crosslinker correlate with its impact on cortical mechanics. Conclusions These observations suggest that myosin-II along with actin Crosslinkers establish local cortical tension and elasticity, allowing for contractility independent of a circumferential cytoskeletal array. Furthermore, myosin-II and actin Crosslinkers may influence each other as they modulate the dynamics and mechanics of cell-shape change.

Stefan Oprea - One of the best experts on this subject based on the ideXlab platform.

  • Novel quinoline-based polyurethane elastomers. The effect of the hard segment structure in properties enhancement
    Journal of Polymer Research, 2011
    Co-Authors: Stefan Oprea
    Abstract:

    Polyurethane elastomers incorporating a quinoline moiety along their polymeric backbones and aliphatic, aromatic or heterocyclic Crosslinkers have been synthesized and characterized. For this, NCO-terminated urethane oligomers were prepared from poly(butylene adipate) diol and methylene diphenyl diisocyanate and were subsequently chain extended with 2,4-quinolinediol and different Crosslinkers. This study reports the influence of the different Crosslinker chemical structures and the hard segment molar ratio on the thermal and dynamic mechanical thermal properties, as well as on the mechanical properties of these elastomers. The fluorescence spectra of polyurethane elastomers were determined at an excitation wavelength of 290 nm. The different chemical structures of the Crosslinkers determine the hard segment cohesion and reduce the mobility of the soft phase, having an important effect on thermal stability and on the mechanical properties of the polyurethane films. Thus the incorporation of aromatic Crosslinkers results in polyurethanes with lower elongation and stress at break. The highest mechanical properties were obtained for polyurethanes crosslinked with aliphatic Crosslinkers.

  • Molecular dynamics, thermo-mechanical and optical studies on benzidine chain extended polyurethane-urea
    Journal of Polymer Research, 2011
    Co-Authors: Stefan Oprea
    Abstract:

    This paper reports the effect that the aromatic diamines and Crosslinker nature have on the physico-mechanical and dielectric properties of linear and crosslinked polyurethane-urea. These elastomers were prepared using poly(tetramethylene glycol) (Terathane 1400), 1,6-hexamethylene diisocyanate and 4,4′-diaminobiphenyl (benzidine) as chain extender and glycerin or castor oil as Crosslinkers. The polyurethane-ureas were characterized through Fourier transform infrared spectroscopy, thermogravimetric analysis, differential dynamic mechanical analysis, dielectric properties. The effects of the hard segments structure on physical, dielectric, mechanical and dynamic mechanical properties of the polyurethane-urea elastomers were investigated. The presence of more urea groups in the hard segment leads to high tensile strength (60–70 MPa), high elongation (700%–950%), increased thermally stability and superior dielectric properties.