Table of Contents

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 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.

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 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.

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 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 (M_w) 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.

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 grouped by mechanism: uncoordinated anionic, coordinated anionic, and cationic.