cet article rappelle les principes de fonctionnement des accumulteurs électrochimiques et de leur utilisation dans note quotidien. Il tente de faire le lien entre ces deux aspects puis met en perspective les developpements scientifiques et technologiques auxquels on peut s'attendre dans le contexte actuel (energie renouvelable, ressources matieres premieres....)

The 14th International Symposium on Electrets (ISE 14) was held at Montpellier (France) during 28-31 August 2011, preceded by a Workshop on the 27th August entitled “Electrets and Related Phenomena in Life Sciences". Both the Symposium and the Workshop were held in historical buildings belonging to the University of Montpellier. The workshop and the symposium attracted 30 and 125 attendees, respectively, from 27 countries. The Symposium attendees were invited to a welcoming party on the evening of Sunday 28th August at the “Maison des Relations Internationales”, hosted by the Montpellier City Council. The scientific program of the Symposium consisted of ten oral and two poster sessions, with a total of 116 contributions distributed over 10 topics. The topics were Charge injection, transport and trapping, Thermally stimulated current and dielectric relaxation, Nanoscale measurements of electrostatic phenomena, Electret phenomena in nanocomposite materials, Ferro-, piezo- and pyroelectric phenomena, Electrostatic and dielectric phenomena in life sciences and bioelectrets, Non-linear electrical and optical effects and photoelectrets, Applications of thin film ferroelectrets, Electrets in organic electronics, and Soft actuators and sensors. Three plenary and ten keynote lectures were given by internationally recognized speakers. In particular, the Gross Memorial Lecture entitled “The legacy of Gross - the analysis and use of long-term phenomena” was given by Professor Jan van Turnout from the Technical University of Delft, The Netherlands. The Dilip Das-Gupta award, which is presented at each ISE for the best presentation by a young scientist or engineer, was shared by Dr. Eric Dantras from the University of Toulouse, France, for his oral presentation “Electroactive properties of polyamide/sodium nobiate nanowires composites” and his contribution to the poster “Thermally stimulated currents: a method to identify gene mutation in Arabidopsis thaliana”, and Dr. Gregorio Faria from the University of Sao Paulo, Brazil, for his oral presentation “Dispersive to non-dispersive transition in the drift mobility of F8BT-based thin-film device” and his poster “Molecular structure and dynamics of F8BT – correlation with opto-electronic properties”. This special issue of the Transaction on Dielectrics and Electrical Insulation (TDEI) gathers papers which are the extended form of some the contributions, oral and poster, presented at ISE 14. After undergoing a meticulous review process, 29 papers were selected to be included in this issue. They represent the state-of-the-art about Electrets Science. As the reader will notice, this science is a truly interdisciplinary subject going from electrical engineering, materials physics and chemistry to biology. As the Chairs of this symposium and guest co-editors of this issue, we aimed at equally covering all this topics with both the fundamental as well as the applied aspects. This editorial gives us the opportunity to deeply thank Ms. Nathalie Cros, Dr. Francois Bauer and Dr. Gilbert Teyssedre who did actively participate in the organization of ISE 14. We would also like to acknowledge Ms. Lydie Berardo, Samira El-Ghazi, Ioana Preda as well as Profs. Colette Lacabanne, Alain Toureille and Jean-Victor Zanchetta and Drs. Eric Dantras and Philippe Molinié for their fruitful help and advice. We are also very grateful to Prof. Takeo Furukawa who was the chairman of ISE 13 and who always positively responded to our questions concerning the organization of the symposium. Likewise, we greatly appreciated Professors Robert Fleming and Reimund Gerhard’s suggestions. Finally, we would like to sincerely thank Ms. Rezi Zarb, IEEE-Dielectrics and Electrical Insulation Society (DEIS) Meetings Chair and Dr. Reuben Hackam, TDEI Editor-in-Chief, for their constant efforts and productive contributions concerning the symposium organization and preparation of this issue, respectively.

Dehydration enthalpy and dc conductivity obtained by means of thermogravimetric analysis and complex impedance spectroscopy respectively on three alkaline-earth, i.e. Mg2+, Ca2+, and Ba2+, exchanged montmorillonites with low water loading are reported. These data are compared with those previously reported on the same montmorillonite exchanged with the whole series of alkali cations, i.e. Li+, Na+, K+, Rb+, and Cs+. A comprehensive analysis of the interplay between the interlayer cations and the adsorbed water molecules is thus made possible regarding both the static, i.e. dehydration enthalpy, and dynamics, i.e. dc conductivity, points of view. It is pointed out that dehydration thermodynamics strongly depends on the cation electrostatic potential energy, whereas the dc conductivity temperature behavior, which turns out to be non-Arrhenian for the most hydrated samples can be remarkably well classified using the cation Jones-Dole viscosity B coefficient.

Purified natural clinoptilolite from the Tasajeras deposit, Cuba, and some of its metal exchanged forms are studied, at the dehydrated state, by means of dielectric relaxation spectroscopy (DRS) using two different modus operandi: complex impedance spectroscopy and dielectric dynamic thermal analysis. Data analysis yields the determination of the extra-framework cation (EFC) population into the various possible crystallographic sites of the zeolitic framework as well as of the activation energy characterizing the localized hopping mechanism of EFC. First, it is shown that the DRS responses obtained here match well with the previous reported data, which were previously localized EFCs in positions close to M1 and M2 sites when the clinoptilolite is modified to almost homoionic form. From this outcome, it can be concluded that all EFCs are in the same crystallographic situation regarding solvation or, in other terms, that no steric effect can be taken into account to explain cationic selectivity. Second, based on the assumption that the activation energy for EFC hopping is directly connected to the EFC/framework interaction and on simple thermodynamics consideration, we show this interaction does not govern the EFC exchange reaction. So, it is emphasized that EFC/H2O interaction is the key factor for cation exchange selectivity.

This paper reports on the one-pot synthesis and characterization of the functionalized mesoporous SBA-15 silica, which contains two loadings of the different acid groups [CO2H, PO(OH)(2) and SO3H]. The thermodynamic features of the water that was confined in these porous silicas was investigated by Differential Scanning Calorimetry (DSC). The results showed that the melting behaviour of the confined water was mainly governed by the pore diameter and, as a consequence, indicated that the chemical "decoration" of the porous surface did not play a key role in the water thermodynamics. On the contrary, the proton conductivity of the hydrated mesoporous materials, which was examined under a wide range of temperatures (-100 to 70 degrees C), was strongly dependent on both the physical state of the confined water and the acidity of the functional groups that were located at the porous surface. The proton conductivity was shown to be directly related to the pK(a) and the density of the functional groups attached to the mesopore surface. The high conductivity values that were obtained at a low temperature when the confined water is frozen, led us to postulate that the SO3H-functionalized SBA-15 sample could be a promising candidate for electrolyte solid applications in fuel cells.

The secondary, ternary and quaternary structures of the biological ion channel Gramicidin-A are investigated by means of UV-visible and fluorescence spectroscopies, and by computational simulations in water/methanol solvent with various molar ratios. Both experiments and molecular dynamics calculations show that the two considered conformations, i.e. the head-to-head and double-stranded β-helix dimers, behave differently with regard to their stability as a function of the methanol content in the water/methanol mixture. To sum-up, calculations show that the double-stranded dimer is stabilized by methanol, even at low content, while the head-to-head dimer conformation breaks into two monomers which remain however coupled whatever the water/methanol mixture. In pure water and low methanol content, the resulting single β-helix structure is maintained due to the stabilization of the channel by water molecules and cations.