Summary: Novel proton conducting ionomers have been prepared by attaching pendant sulfonated aromatic side chains to polysulfone. Lithiated polysulfone was first reacted with 4‐fluorobenzoic acid chloride to introduce 4‐fluorobenzoyl side chains to the polymer main chain. Next, the activated fluoro groups were replaced by 4‐sulfophenoxy or 7‐sulfo‐2‐naphthoxy in a potassium carbonate‐mediated nucleophilic substitution reaction. This reaction proceeded under full conversion and the degree of substitution was easily controlled by the degree of lithiation in the first step. Membranes based on ionomers carrying one sulfophenoxybenzoyl unit per polymer repeat unit reached a proton conductivity exceeding 30 mS · cm−1 at 120 °C under immersed conditions.Structures of sulfophenoxybenzoyl polysulfone and sulfonaphthoxybenzoyl polysulfone.magnified imageStructures of sulfophenoxybenzoyl polysulfone and sulfonaphthoxybenzoyl polysulfone.

No abstract

Membrane electrode assemblies ͑MEAs͒ with a sulfonated polysulfone ͑sPSU͒ as the proton-conducting phase were fuel cell evaluated at varying temperatures in over-humidified conditions. The sPSU was prepared by a direct polycondensation involving a commercially available sulfonated naphthalene diol monomer. The gas diffusion electrodes ͑GDEs͒ and MEAs were successfully fabricated and a thorough morphological study was subsequently carried out on GDEs with varying sPSU contents and ink solvents. The scanning electron microscopy and porosimetry studies revealed highly porous GDE morphologies at sPSU contents below 20 wt %. Double-layer capacitance measurements showed an almost fully sPSU-wetted electronic phase when the sPSU content was 10 wt %. The MEAs were prepared by applying the GDEs directly onto sPSU membranes. MEAs with a total Pt loading of 0.2 mg/cm 2 were successfully fuel cell operated at 120°C. The MEAs showed mass-transport limitations in the range of 600-800 mA/cm 2 , most probably caused by abundant water due to the overhumidified measuring conditions. The low resistance of the MEAs indicated a well-integrated structure between the GDEs and the membrane.The research on membrane materials for the proton exchange membrane fuel cell ͑PEMFC͒ and the direct methanol fuel cell ͑DMFC͒ has expanded in the last ten years. 1 The focus has been on developing membranes with high conductivity, low reactant permeability, and high mechanical and thermal stability. 1-3 The goal has also been to develop low-cost materials for high-temperature and low-humidity applications. 4 The current cost of the state-of-the-art membranes and other components used in commercial fuel cell stacks is high, and an important requirement is therefore the reduction of the capital cost of the system. 4 The high-temperature operation requires either a membrane with a nonhydrous proton conduction mechanism, or a pressurized system. PEMFC operation at increased temperatures, 120-130°C, has several advantages: the carbon monoxide tolerance of the platinum catalyst is increased, which makes it possible to use reformate fuels; the size of required cooling system is decreased; and the quality of generated heat is improved. However, there are problems related to the increased temperature such as the need for pressurization of the system and an accelerated carbon support degradation. Several aromatic polymers including polyetherketones ͑PEK͒, polyetheretherketones ͑PEEK͒, polyethersulfones ͑PES͒, and polysulfones ͑PSU͒ have been investigated as potential proton-conducting membrane materials. 1 Sulfonated polysulfones ͑sPSU͒ have been shown to be suitable for PEMFC applications due to their good thermal and mechanical stability, and also due to readily available, low-cost monomers and polymers. [5][6][7] The potential of the material is strengthened by the results reported by Ekström et al., which showed unchanged performance of the sPSU membrane after 300 h in situ fuel cell testing. 8 Furthermore, many of the merits of sPSU as fuel cell membrane ...

No abstract

Polymerisation of trimethylene carbonate (TMC) and its copolymerisation with L‐lactide (LA) using the SmI2/Sm initiator system is reported. The reactions were carried out at different temperatures to optimize the reaction conditions. Reactivity ratio values evaluated using the Kelen–Tüdos method were 7.24 and 0.25 for LA and TMC, respectively. Microstructure of the copolymers and its change with the reaction time is reported using 1D (1H and 13C) and 2D heteronuclear multiple‐bond correlation NMR spectroscopic techniques. Electrospinning of the resulting copolymers was tried for the generation of fibres. Drastic deviations of the thermodynamic state from equilibrium were seen in the first heating cycle of the DSC trace of the electrospun fibres and are also reported here. Copyright © 2005 Society of Chemical Industry