PC)Co(PPh3), where X = /7-OCH3, p-CH3, p-C 1, m-Cl, m-F, o-Cl, o-F, or H, were synthesized and characterized in nonaqueous media using electrochemical, spectroelectrochemical, and EPR techniques. The o-Cl derivative exists as different atropisomers in solution, and a thermal interconversion between them was achieved at 338 K in toluene. Activation parameters (AS*, AH*) for interconversion between the atropisomers were obtained from NMR measurements and were similar in magnitude to values reported for ortho-substituted tetraphenylporphyrin derivatives. Formation constants for pyridine binding to the pentacoordinated cobalt(III) corroles in benzene were obtained from UV-visible spectrophotometric measurements and ranged between 20 and 193 M-1, with the exact value depending upon the specific electron-donating or electron-withdrawing group on the three phenyl rings of the complex. The redox potentials of (OMTXPC)Co(PPh3) also shift with the nature of the phenyl ring substituents, and linear ffee-energy relationships are observed. Each cobalt(III) derivative undergoes two oneelectron reductions, the first of which involves a Co(IH)/Co(II) conversion and concomitant loss of the bound PPI13 ligand. Four one-electron oxidations are also observed for the investigated compounds, and this contrasts with the oxidative properties of related cobalt(II) porphyrins which undergo a maximum of three one-electron oxidations under similar solution conditions. The first one-electron oxidation of each cobalt(III) corrole is metalcentered and results in formation of a Co(IV) corrole as ascertained by EPR spectroscopic characterization of the electrogenerated species.

Sulfonated poly(ether ether ketone) (SPEEK) membranes were thermally treated at temperatures between 120 and 160°C. Water uptake measured at different relative humidity values or by full immersion in water between 25 and 145°C was found to depend very strongly on previous thermal treatment and casting solvent. Water-uptake coefficient values as low as 10-15 even upon immersion in water at 100°C were obtained with membranes treated at 160°C. This effect is related to cross-linking by SO 2 bridges between macromolecular chains. An important role is also played by the casting solvent: among the investigated solvents, dimethylsulfoxide (DMSO) gave the best results. A chemical kinetics model is outlined that permits the estimation of the relevant kinetic parameters, especially the activation energy of the cross-linking reaction, which was found to be about 60 kJ/mol. These results are of significant importance for the improvement of proton-exchange membrane fuel cells. IntroductionThe current trend toward environmentally friendlier and more efficient power production has shifted the bias from conventional fuels and internal combustion engines toward alternative fuels and power sources. Much interest is focused on developing proton-exchange membrane fuel cells (PEMFCs), which use a polymer membrane as the electrolyte. The future application of this type of technology depends greatly on the enhancement of membrane stability. The polymer electrolyte membrane must be improved in terms of durability; most importantly, it must be compatible with operation at temperatures of around 130°C (intermediate temperature) at low relative humidity (RH) for H 2 fuel cells, and it must present a reduced fuel crossover for direct methanol fuel cells (DMFCs).1,2 The objective is to reduce membrane swelling at high relative humidity and, in the framework of intermediate-temperature fuel cells, to reduce the degradation of properties observed during fuel cell operation at higher temperature.

a b s t r a c tThermal stability, hydration and mechanical properties of thermally cross-linked sulfonated aromatic polymers (SAP) with high ionic exchange capacity (IEC) were measured and compared to untreated samples. The formation of cross-linking greatly stabilizes sulfonated polyphenylsulfone (SPPSU) in terms of thermal, mechanical, and hydrolytic degradation: it can resist in water even at a temperature of 145• C with improved mechanical properties, while TGA experiments demonstrate that SPPSU membranes are stable well above 200• C. Sulfonated polyethersulfone (SPES) membranes show, instead, a hydrolytic instability.

An important step in the synthesis of hybrid materials is the control of organic chains formation when the organically modified alkoxides are bearing polymerizable groups, such as acrylate or epoxy. Control of the process can be achieved through a deep understanding of the correlation between the synthesis parameters and the final structure. In this paper we have used 3-methacryloxypropyltrimethoxysilane (MPTMS) co-hydrolyzed with tetraethyl orthosilicate (TEOS) using 3-aminopropyltriethoxysilane (APTS) as basic catalyst and network modifier of the structure. The acrylate function in MPTMS has been thermally polymerized and the process has been tuned, with the purpose to reach the highest polymerization efficiency, by controlling the synthesis parameters. The synthesis has been followed in solution by 13 C and 29 Si nuclear magnetic resonance (NMR) spectroscopy, and the structural changes in the films have been studied by Fourier transform infrared spectroscopy (FTIR) as a function of the thermal treatment. Multinuclear solid state NMR spectroscopy on related bulk materials has provided supplementary information on the hybrid network formation. As-deposited films are not fully condensed but a very large conversion of the CdC double bonds (up to 98% of polymerization degree) is achieved during thermal curing by the simultaneous inorganic polycondensation and organic polymerization.

The development of proton exchange membranes as electrolytes for polymer electrolyte fuel cells operating at intermediate temperatures has been achieved combining two approaches: the preparation of a cross-linked polymer and the formation of covalent organic/inorganic hybrids. A covalently crosslinked sulfonated polyetheretherketone with elevated degree of sulfonation (DS ) 0.8) was prepared by reaction with HSO 3 Cl (SOPEEK). No degradation of PEEK was detected upon sulfonation, but only cross-linking via sulfonic groups with formation of SO 2 moieties was observed. The extent of ramification was calculated by analyzing the 1 H nuclear magnetic resonance (NMR) spectra of the products and resulted in 20% of the total amount of -SO 3 H groups present in the polymer. The solubility of the -SO 2 Cl precursor in organic solvents allowed easy carrying out of functionalization reactions in homogeneous conditions by lithiation and subsequent reaction with SiCl 4 , thus introducing covalenly linked silicon moieties (SOSiPEEK) at the ratios 1:0.25 and 1:0.50 per monomeric unit. The products were characterized by 1 H and 13 C NMR, attenuated total reflectance Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry.

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a b s t r a c tThe mechanical properties of sulfonated aromatic polymers (SAPs: SPEEK and SPPSU) are studied by tensile stress-strain tests and dynamic mechanical analysis (DMA). The elastic moduli are generally above 1 GPa with tensile strength between 25 and 80 MPa and elongation at rupture between 7 and 50%. These properties are consistent with polymers below their glass transition temperature. The glass transition and elastic moduli are strongly increased by thermal treatments of the SAP membranes, due to formation of cross-links between macromolecules. The cross-linking is observed "in situ" during DMA experiments on thermally untreated SPPSU. These data show that previously neglected SAPs might become very interesting PEM fuel cell membranes, if previously thermally treated.

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