Sébastien Maria

Single-ion BAB triblock copolymers as highly efficient electrolytes for lithium-metal batteries

Electrochemical energy storage is one of the main societal challenges of this century. The performances of classical lithium-ion technology based on liquid electrolytes have made great advances in the past two decades, but the intrinsic instability of liquid electrolytes results in safety issues. Solid polymer electrolytes would be a perfect solution to those safety issues, miniaturization and enhancement of energy density. However, as in liquids, the fraction of charge carried by lithium ions is small (<20%), limiting the power performances. Solid polymer electrolytes operate at 80 °C, resulting in poor mechanical properties and a limited electrochemical stability window. Here we describe a multifunctional single-ion polymer electrolyte based on polyanionic block copolymers comprising polystyrene segments. It overcomes most of the above limitations, with a lithium-ion transport number close to unity, excellent mechanical properties and an electrochemical stability window spanning 5 V versus Li(+)/Li. A prototype battery using this polyelectrolyte outperforms a conventional battery based on a polymer electrolyte.

Separation of Parent Homopolymers from Polystyrene-b-poly(ethylene oxide)-b-polystyrene Triblock Copolymers by Means of Liquid Chromatography: 1. Comparison of Different Methods

Separation of parent homopolymers, polystyrene and poly(ethylene oxide), from the triblock copolymer polystyrene-b-poly(ethylene oxide)-b-polystyrene was investigated by means of liquid chromatography techniques. Overall suitability was evaluated and compared for size exclusion chromatography, (SEC), liquid chromatography under critical conditions of enthalpic interactions (LC CC), and liquid chromatography under limiting conditions of desorption (LC LCD). Among these techniques, LC LCD was the only one able to fully separate block copolymers from both their parent homopolymers in one single run. The efficiency of the separation was proven by (1)H NMR analysis of previously collected fractions.

Enhanced electrochemical performance of Lithium-ion batteries by conformal coating of polymer electrolyte

This work reports the conformal coating of poly(poly(ethylene glycol) methyl ether methacrylate) (P(MePEGMA)) polymer electrolyte on highly organized titania nanotubes (TiO2nts) fabricated by electrochemical anodization of Ti foil. The conformal coating was achieved by electropolymerization using cyclic voltammetry technique. The characterization of the polymer electrolyte by proton nuclear magnetic resonance (1H NMR) and size-exclusion chromatography (SEC) shows the formation of short polymer chains, mainly trimers. X-ray photoelectron spectroscopy (XPS) results confirm the presence of the polymer and LiTFSI salt. The galvanostatic tests at 1C show that the performance of the half cell against metallic Li foil is improved by 33% when TiO2nts are conformally coated with the polymer electrolyte.

Influence of Pyrene Grafting on PMMA Nanosecond Laser Ablation at 248 nm

In this work, we investigate the effects of KrF nanosecond laser ablation on poly(methyl methacrylate) (PMMA) in combination with pyrene. Three materials containing PMMA were studied: (1) one doped with pure pyrene, (2) one doped with methyl 3-(1-pyrenyl)propanoate (so called alkylpyrene derivative thereafter), and (3) one grafted with pyrene. This last new material was developed by covalently bonding pyrene molecules to PMMA side-chains. A comparative study was undertaken to determine and compare the respective properties of the PMMA dye containing pyrene during nanosecond laser ablation at 248 nm. Cavities were etched for each material with up to 20 pulses for fluences between 0.03 and 1.7 J/cm(2) in samples containing 1, 2, and 4 mol % chromophore. The threshold fluences and the effective absorption coefficients were obtained. It was observed that effective absorption coefficients increased and threshold fluences decreased with the chromophore percentages in each kind of sample. Ablation parameters were not significantly modified when the dopant was changed from pyrene to the alkylpyrene derivative. On the other hand, when pyrene molecules were grafted on the polymer, the threshold fluences decreased, whereas the effective absorption coefficients became similar at fluences above 0.6 J/cm(2).

Separation of parent homopolymers from polystyrene and poly(ethylene oxide) based block copolymers by liquid chromatography under limiting conditions of desorption-3. Study of barrier efficiency according to block copolymers' chemical composition.

Liquid Chromatography under Limiting Conditions of Desorption (LC LCD) is a powerful separation tool for multicomponent polymer systems. This technique is based on a barrier effect of an appropriate solvent, which is injected in front of the sample, and which decelerates the elution of selected macromolecules. In this study, the barrier effects have been evaluated for triblock copolymers polystyrene-b-poly(ethylene oxide)-b-polystyrene (PS-b-PEO-b-PS) according to the content of polystyrene (wt% PS) and PEO-block molar mass. PS-b-PEO-b-PS samples were prepared by Atom Transfer Radical Polymerization (ATRP). The presence of respective parent homopolymers was investigated by applying optimized LC LCD conditions. It was found that the barrier composition largely affects the efficiency of separation and it ought to be adjusted for particular composition range of block copolymers.

Reworkable layered silicate-epoxy nanocomposites: synthesis, thermomechanical properties and combustion behaviour

Abstract Epoxy resin/montmorillonite nanocomposites were obtained via in situ intercalative polymerisation. The polymer matrix consists of anhydride-cured epoxy, and the choice of catalyst allows exchange reactions without depolymerisation. This makes the resin insoluble and reprocessable at the same time and potentially recyclable. In this study, reprocessing of the nanocomposites was done by mechanical grinding and re-welding by compression moulding at high temperature, similarly to thermoplastics. The effect of this process on the level of clay dispersion is discussed. Nanocomposite superstructures were imaged by means of transmission electron microscopy, and montmorillonite interlayer spacings were estimated by small angle X-ray scattering. The thermomechanical and combustion properties of the nanocomposites were investigated by means of dynamic mechanical thermal analysis, thermogravimetric analysis and cone calorimetry. The material tensile complex modulus E* was improved by nanocomposite formation, also after the glass transition occurred. Flammability of the material was moderately affected by the dispersed clay.

Chapter 8:Complex Macromolecular Architectures Prepared by NMP

Nitroxide-mediated polymerization (NMP), being a reversible deactivation radical polymerization (RDRP) technique, has been the subject of considerable attention in polymer science. Lavishly granting access to well-defined and highly functional polymers, NMP has paved a huge avenue for complex macromolecular architectures. This book chapter highlights these structures prepared by NMP comprising linear as well as non-linear topologies. The different synthetic approaches relevant to these topologies are outlined, giving a broad overview of the potentialities of NMP in advanced polymer synthesis.