Crosslinked SPEEK membranes: Mechanical, thermal, and hydrothermal properties

The thermal and mechanical behavior, the water uptake (WU), and water diffusion coefficient of sulfonated poly(ether ether ketone) (SPEEK)membranes annealed at 180 degrees C for different times were explored by high-resolution thermogravimetric analysis, mechanical tensile tests, dynamic mechanical analysis, and WU measurements. The mechanical and thermal stability increased with the thermal treatment time, i.e., with the degree of crosslinking. The effect of residual casting solvent, dimethyl sulfoxide (DMSO), on the WU within SPEEK was probed. In presence of residual DMSO, crosslinked SPEEK exhibited higher water sorption at low and medium relative humidity (RH), and lower water sorption at high RH. These membranes have properties well adapted to fuel cell applications

Association between hearing sensitivity and dopamine transporter availability in Parkinson's disease

In a previous study, we observed: significant hearing function impairment, assessed with pure tone audiometry and distortion product otoacoustic emissions, in patients with Parkinson's disease, compared with a matched control group, and lateralization of the hearing dysfunction, worse on the side affected by more pronounced Parkinson's disease motor symptoms. This study investigates the association between the basal ganglia dopamine transporter availability and the hearing function in Parkinson's disease patients, focusing also on the lateralization of both dysfunctions, with respect to that of the motor symptoms, and introducing a further distinction between patients with left-sided and right-sided predominant motor symptoms. Patients with right-handed Parkinson's disease with a recent estimation of 123I-FP-CIT striatal uptake were audiologically tested with pure tone audiometry and distortion product otoacoustic emissions. Thirty-nine patients were included in the study. A statistically significant association was found, in the left-side predominant group only, between the distortion product otoacoustic emission levels and the contralateral dopamine transporter availability, and between the hearing threshold and the dopamine transporter availability difference between the ipsi- and the contralateral sides. The hearing impairment lateralization correlated to the motor symptom asymmetry was found significant only in the left-side predominant patients. The association between hearing function and basal ganglia dopamine transporter availability supports the hypothesis that the peripheral hearing function decline associated with dopamine depletion is involved in Parkinson's disease development, with a significant difference between patients with left- and right-sided predominant motor symptoms. These findings also suggest that peripheral hearing function evaluation and its lateralization could be key elements for subtyping the disease

Effects of different dietary amounts of LCPUFA n3 and vitamin B6 on lipid composition and antioxidant defences in rat kidney.

Our previous report demonstrated that, when vitamin deficiency is associated with high contents of long chain polyunsaturated fatty acids (LCPUFA) n3, lipid peroxidation susceptibility in rat heart and liver increases. In this paper, we evaluated the effect of the same dietary administration on lipid composition and antioxidant defenses of rat kidney. Results showed that vitamin B6 deficiency, when associated with a fish oil diet, as compared to vegetable oil condition, increased relative kidney weight and decreased pyridoxal-5P contents. The different LCPUFA n3 dietary contents produced, on kidney phospholipids, effects interlaced with those of vitamin B6 deficiency; in particular fish oil and vitamin B6 deficient diet caused a significant decrease of arachidonic acid showing that the processes of elongation and desaturation of linoleic acid were slowed. Also, peroxidation susceptibility was higher, as demonstrated both by increased TBARS formation and glutathione peroxidase activity, and by decreased vitamin E contents and reduced glutathione/oxidized glutathione ratio

Proton Mobility in Sulfonated PolyEtherEtherKetone (SPEEK): Influence of Thermal Crosslinking and Annealing

Sulfonated PolyEtherEtherKetone (SPEEK) was thermally treated at 180 and 140 degrees C to study the effects of polymer cross-linking and annealing on the water uptake and proton conductivity. The kinetics of the cross-linking reaction can be quantitatively described with an activation energy of (100 +/- 2)kJ/mol. The proton mobility u(H+) depends on the proton concentration c(H+) in excellent agreement with the power law u(H+) = c(H+)3 observed above the percolation threshold of hydrated nanometric channels. The proton mobility can be described by porosity and tortuosity as phenomenological parameters. Polymer annealing reduces the free volume and porosity of membranes. The proton conductivity can be modulated by changing the hydration number

Properties of composite membranes of SPEEK and nanodiamond

The manufacture of composite materials can improve the properties of proton-conducting polymers as membranes in PEM fuel cells. We have investigated composite membranes obtained by dispersion of nanodiamond particles in a sulfonated PolyEtherEtherKetone (SPEEK) matrix. SPEEK is a major proton-conducting aromatic polymer. Nanodiamond has been studied for various applications and can be functionalized with different surface groups. For use in proton-conducting membranes, surface functionalization with proton-donating groups is a promising approach. In this preliminary work, we have studied the properties of membranes made using pristine nanodiamond from diverse origins for a first assessment of the potential properties. The composites were analysed by various techniques, including Thermogravimetric Analysis, water vapor uptake and mechanical tensile tests. © 2012 Materials Research Society

Cross-Linking of Sulfonated Poly(ether ether ketone) by Thermal Treatment: How Does the Reaction Occur?

The cross-link reaction between macromolecular chains of sulfonated poly(ether ether ketone) (SPEEK) by thermal treatment above 150 degrees C in presence of dimethylsulfoxide (DMSO) is investigated by various techniques, including elemental analysis, acid-base titration, infrared spectroscopy, water uptake (WU) measurements, and thermogravimetry. The conditions of thermal treatment are analyzed. The cross-linking reaction occurs in at least three more or less activated and deactivated positions with different activation energies, leading to different time dependencies of the cross-link reaction. The role of residual solvent DMSO is studied particularly: the cross-linking depends significantly on the amount of solvent in the membranes. Implications on WU and thermal stability are of particular importance for the development of high performance proton-conducting membranes