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Polymers, Volume 4, Issue 4 (December 2012), Pages 1627-1686

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Research

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Open AccessArticle Influence of Ionomer/Carbon Ratio on the Performance of a Polymer Electrolyte Fuel Cell
Polymers 2012, 4(4), 1645-1656; doi:10.3390/polym4041645
Received: 16 August 2012 / Revised: 12 November 2012 / Accepted: 13 November 2012 / Published: 20 November 2012
Cited by 5 | PDF Full-text (1844 KB) | HTML Full-text | XML Full-text
Abstract
We have used fibrous carbon materials as polymer electrolyte fuel cell (PEFC) electrodes. We have examined the influence of the ionomer/carbon ratio on the performance of the PEFCs. The Marimo carbon is a kind of carbon with a spherical shape, and consists [...] Read more.
We have used fibrous carbon materials as polymer electrolyte fuel cell (PEFC) electrodes. We have examined the influence of the ionomer/carbon ratio on the performance of the PEFCs. The Marimo carbon is a kind of carbon with a spherical shape, and consists of carbon nanofilaments. Fibrous carbon materials have large specific surface areas without fine pores. The reactant gases and generated water can easily diffuse among the nanofilaments. The ionomer plays two roles; one is a proton transfer activity, and the other is binding the catalyst electrodes. An excess ionomer interferes with the diffusion of gases. The ionomer/carbon ratio should affect the performance of the PEFC, especially at a high current density. Full article
(This article belongs to the Special Issue Polymers for Fuel Cells & Solar Energy)
Open AccessArticle Ring Opening Metathesis Polymerization of Norbornene and Derivatives by the Triply Bonded Ditungsten Complex Na[W2(µ-Cl)3Cl4(THF)2]·(THF)3
Polymers 2012, 4(4), 1657-1673; doi:10.3390/polym4041657
Received: 7 October 2012 / Revised: 10 November 2012 / Accepted: 14 November 2012 / Published: 21 November 2012
Cited by 8 | PDF Full-text (281 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
In this study, the reactions of the bimetallic compound Na[W2(µ-Cl)3Cl4(THF)2]·(THF)3 (1, (W 3 W)6+, a'2e'4) with norbornene (NBE) and some of [...] Read more.
In this study, the reactions of the bimetallic compound Na[W2(µ-Cl)3Cl4(THF)2]·(THF)3 (1, (W 3 W)6+, a'2e'4) with norbornene (NBE) and some of its derivatives (5-X-2-NBE; X = COOH (NBE–COOH), OH (NBE–OH), CN (NBE–CN), COOMe (NBE–COOMe), CH=CH2 (VNBE); norbornadiene (NBD)) are described. Complex 1 contains a tungsten–tungsten triple bond, bearing three halide bridges and two labile THF ligands, in a cisoidal relationship along the metal–metal axis. The complex was found to be a highly efficient room temperature homogeneous and heterogeneous unicomponent initiator for the catalytic ring opening metathesis polymerization (ROMP) of most substrates. NBE provides polynorbornene (PNBE) of high molecular weight (Mw) in high yields, soluble in organic solvents. The reaction proceeds with high cis-stereoselectivity (80%–86% cis), independently of the reaction conditions. Strongly coordinating pendant groups (–COOH, –OH, –CN) deactivate 1, whereas substrates bearing softer ones (–COOMe, –CH=CH2) are quantitatively polymerized. NBD gives quantitatively insoluble PNBD. The polymers have been characterized by 1H, 13C NMR and Size Exclusion Chromatography (SEC). Monitoring the reactions in situ by 1H NMR (1/NBD or NBE) provides direct evidence of the metathetical nature of the polymerization with the observation of the active tungsten alkylidene propagating polymeric chains. Mechanistic aspects of the reactions are discussed. Full article
(This article belongs to the Special Issue Ring-Opening Polymerization)
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Review

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Open AccessReview Novel Blend Membranes Based on Acid-Base Interactions for Fuel Cells
Polymers 2012, 4(4), 1627-1644; doi:10.3390/polym4041627
Received: 20 August 2012 / Revised: 25 September 2012 / Accepted: 26 September 2012 / Published: 11 October 2012
Cited by 22 | PDF Full-text (1519 KB) | HTML Full-text | XML Full-text
Abstract
Fuel cells hold great promise for wide applications in portable, residential, and large-scale power supplies. For low temperature fuel cells, such as the proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs), proton-exchange membranes (PEMs) are a key component [...] Read more.
Fuel cells hold great promise for wide applications in portable, residential, and large-scale power supplies. For low temperature fuel cells, such as the proton exchange membrane fuel cells (PEMFCs) and direct methanol fuel cells (DMFCs), proton-exchange membranes (PEMs) are a key component determining the fuel cells performance. PEMs with high proton conductivity under anhydrous conditions can allow PEMFCs to be operated above 100 °C, enabling use of hydrogen fuels with high-CO contents and improving the electrocatalytic activity. PEMs with high proton conductivity and low methanol crossover are critical for lowering catalyst loadings at the cathode and improving the performance and long-term stability of DMFCs. This review provides a summary of a number of novel acid-base blend membranes consisting of an acidic polymer and a basic compound containing N-heterocycle groups, which are promising for PEMFCs and DMFCs. Full article
(This article belongs to the Special Issue Polymers for Fuel Cells & Solar Energy)
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Open AccessReview Synthesis and Polymerizability of Atom-Bridged Bicyclic Monomers
Polymers 2012, 4(4), 1674-1686; doi:10.3390/polym4041674
Received: 11 September 2012 / Revised: 19 November 2012 / Accepted: 20 November 2012 / Published: 5 December 2012
PDF Full-text (227 KB) | HTML Full-text | XML Full-text
Abstract
¨The synthesis and polymerizability of atom-bridged bicyclic monomers was surveyed. The monomers included lactams, ureas, urethanes, lactones, carbonates, ethers, acetals, orthoesters, and amines. Despite widely-varying structures, they almost all polymerized to give polymers with monocyclic rings in the chain. The polymerizations are [...] Read more.
¨The synthesis and polymerizability of atom-bridged bicyclic monomers was surveyed. The monomers included lactams, ureas, urethanes, lactones, carbonates, ethers, acetals, orthoesters, and amines. Despite widely-varying structures, they almost all polymerized to give polymers with monocyclic rings in the chain. The polymerizations are grouped by mechanism: uncoordinated anionic, coordinated anionic, and cationic. Full article
(This article belongs to the Special Issue Ring-Opening Polymerization)
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