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[en] Highlights: • Substitution of the polymer backbone with perfluorosulfonic acid in one step. • Design of ionomers with very hydrophobic backbone. • The ionomers show better proton conducting properties than the Nafion. • The ionomers show moderate water uptake even at high ion exchange capacity. - Abstract: The publication reports, for the first time, on the synthesis of aromatic-based ionomers bearing superacid side groups bonded to a highly hydrophobic fluorinated aromatic backbone. The incorporation of the side group on the backbone takes place in one step via a nucleophilic substitution. The membranes obtained from these new ionomers show phase separation at nanoscale and moderate water uptake even at high ion exchange capacity (IEC), i.e. 1.7 meq/g. Additionally, their conductivity and mechanical strength are much higher than those of the benchmarked ionomer Nafion®, which makes them very promising materials for fuel cell application.
[en] The study deals with the electrochemical and physico-chemical characterizations of new proton-conducting ionic liquids. Through the use of several amines and perfluorinated acids, it attempts to define the most appropriate ionic liquids for use in high temperature PEMFCs. In addition to the usual characterizations based on Pulsed Field Gradient NMR and conductivity measurements, NMR correlation techniques NOESY, HOESY and COSY experiments are used to characterize the interactions and spatial proximities of ionic liquid species
[en] This paper examines the behaviour of lithium polymer electrolytes based on aromatic sulfonamide salts tailored to optimize negative charge delocalization through the aromatic ring and up to the nitro substituents located in the para and para/ortho positions of the nitrogen of the sulfonamide anion. For the first time, lithium salt dissociation has been connected to the Σ+ value. Thanks to the tailoring of these anions and to this physico-chemical approach it has been possible to show that resonance electron-withdrawing effects, as opposed to inductive ones, are decisive in reaching high conductivities in aprotic polymer electrolytes. Moreover the dissociation enhancement that can be expected, using the Σ+ value of NO2, from the introduction of an additional nitro group, is in good agreement with the conductivity enhancement.
[en] Nanocomposite materials were obtained from poly(vinylidene fluoride) (PVdF) as matrix polymer and a stable DMF suspension of nanocrystalline cellulose (NCC) as the reinforcing phase. Porous and dense nanocomposite membranes were prepared by non-solvent induced phase separation (NIPS) and film casting methods, respectively. The resulting films were characterized regarding their structuration, i.e., the content of crystalline phases, as well as their transport and thermo-mechanical properties. The presence of the fillers led to a mechanical reinforcement, associated with a lower strain at break. For dense nanocomposites, a thermal stabilization at temperatures higher than the melting temperature was highlighted and ascribed to the formation of a rigid cellulosic network within the matrix. The superior electrochemical performances together with the observed reinforcement effect render these porous nanocomposites membranes as interesting candidates for the replacement of commercial polyolefin-based microporous separators in lithium-ion batteries.
[en] ABSTRACT: Electrolyte compositions based on LiTFSI dissolved in fluorinated linear and cyclic carbonates were characterized regarding their transport and thermal properties, viscosity, solvation ability, electrochemical stability towards oxidation, as well as their ability to inhibit the aluminum current collector corrosion. As a result of the thorough investigation, different binary mixtures were prepared, which offer beneficial properties in terms of aluminum current collector protection and provide optimized transport properties. The use of LiTFSI as electrolyte salt rather than the state-of-the-art lithium salt, LiPF_6, enables substantial improvements with respect to safety, while maintaining high performance liquid electrolyte
[en] The objective of this work is to present the behavior of a fluorinated microporous membrane composed of poly(vinylidene fluoride) (PVDF) mechanically reinforced by a polyamide-66 (PA-66) fabric under γ-irradiation with dose ranging between 0 and 100 kGy, in inert atmosphere and at room temperature. Particular attention was paid to the evolution of mechanical properties, the surface morphology and pores size distribution of this membrane, in order to study the filtration capacity and selectivity with increasing radiation dose. Moreover, the repartition of the generated radicals onto the two components of the membrane was achieved by electron spin resonance (ESR) spectroscopy. Two different regimes are observed depending on the dose range, and a correlation between the mechanical behavior of the membrane and the evolution of the concentration of the radicals in the PA fabric is observed. Globally, the porosity of the surface membrane does not vary whatever the dose may be, but the mechanical properties of the membrane as well as the permeability are strongly affected, even for low radiation dose such as 10 kGy. These results are related to chain scissions on the PA fabric, which occurred preferentially, compared to cross-linking, in the investigated dose range. - Highlights: ► γ-irradiation of PA-66 reinforced PVDF microfiltration membrane. ► Dose range, between 10 and 100 kGy, investigated. ► Porosity of the membrane constant upon irradiation. ► Mechanical properties and permeability strongly affected due to chain scissions on PA-66.