• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 3
  • 2
  • 1
  • Tagged with
  • 9
  • 9
  • 4
  • 4
  • 4
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Lithium transport in crown ether polymers

Collie, Luke E. January 1995 (has links)
A series of 12-, 13-, and 14-membered crown ether rings bearing polymerisable side-chains has been synthesised. The crown ethers were attached to a methacrylate or acrylate polymerisable group either via a short link (Ring-CH(_2)-O-Polymer) or via a spacer group. Both hydrocarbon and ethylene oxide spacer groups were used, giving structures of the form (Ring-CH(_2)-O-(CH(_2))(_6)-O-Polymer) and (Ring-CH(_2)-O-((CH(_2)CH(_2))(_2)O)-Polymer). The ethylene oxide chain can potentially bind to a Li(^+) dopant ion. The relative Li(+) binding affinity of 12-, 13-, and 14-membered mono- and disubstituted crown ethers has been assessed by variable temperature (^13)c and (^7)Li NMR. The crown ether bearing monomers were polymerised using standard free-radical polymerisation methods to yield amorphous materials whose glass transition temperature (T(_g)) was controlled principally by the nature of the spacer group. On doping with lithium triflate (LiCF(_3)SO(_3)), the polymers exhibit high ionic conductivity. The conductivity was primarily dependent on polymer T(_g), but was also found to be higher for 12-crown-4 based systems than for 13-crown-4 and 14-crown-4 based analogues. This behaviour was consistent with the results of the NMR studies, which showed that Li(^+) exchange occurs more readily between 12-crown-4 rings than 13- or 14-crown-4 rings. The NMR studies also showed that 12-crown-4 systems have a higher tendency to form 2:1 (ring : Li(^+)) complexes. Within a polymer matrix, the presence of 2:1 complexes allows Li(^+) migration via an association-disassociation mechanism, avoiding the high energy intermediate state of a free or weakly bound Li(^+) ion. The greater encapsulation provided by 2:1 complexation may also aid in ion pair separation.
2

Computational study of the transport mechanisms of molecules and ions in solid materials

Zhang, Yingchun 02 June 2009 (has links)
Transport of ions and molecules in solids is a very important process in many technological applications, for example, in drug delivery, separation processes, and in power sources such as ion diffusion in electrodes or in solid electrolytes. Progress in the understanding of the ionic and molecular transport mechanisms in solids can be used to substantially increase the performance of devices. In this dissertation we use ab initio calculations and molecular dynamics simulations to investigate the mechamisn of transport in solid. We first analyze molecular transport and storage of H2. Different lightweight carbon materials have been of great interest for H2 storage. However, pure carbon materials have low H2 storage capacity at ambient conditions and cannot satisfy current required storage capacities. Modification of carbon materials that enhance the interaction between H2 and absorbents and thus improve the physisorption of H2, is needed for hydrogen storage. In this dissertation, corannulene and alkali metal-doped corannulene are investigated as candidate materials for hydrogen storage. Molecularalso investigated. Using computational chemistry, we predict enhanced H2 adsorption on molecular systems with modification and hydrogen uptake can reach DOE target of 6.5wt% at at 294 bar at 273 K, and 309 bar at 300 K. In the second part of this dissertation, we study the lithium ion transport from a solid electrolyte phase to a solid electrode phase. Improvement of ionic transport in solid electrolytes is a key element in the development of the solid lithium ion batteries. One promising material is dilithium phthalocyanine (Li2Pc), which upon self-assembly may form conducting channels for fast ion transport. Computational chemistry is employed to investigate such phenomena: (1) to analyze the crystalline structure of Li2Pc and formation of conducting channels; (2) to understand the transport of Li ions inside channels driven by an electric field; (3) to study the continuity of the conducting channels through interface. The study shows Li2Pc has higher conductivity than PEO as electrolyte.
3

Preparation, Characterization, and Application of Molecular Ionic Composites for High Performance Batteries

Yu, Deyang 03 November 2021 (has links)
A solid electrolyte is a crucial component of any solid state battery. Polymer gel electrolytes have received increasing attention in recent years due to their high ionic conductivity, flexibility, and improved safety. However, a general tradeoff usually exists between the mechanical properties and ionic conductivity in such materials. Molecular ionic composites (MICs) are a new type of rigid polymer gel electrolyte based on ionic liquids (ILs) and a double helical rigid-rod polyamide, poly(2,2′-disulfonyl-4,4′-benzidine terephthalamide) (PBDT). MICs have high ionic conductivity, high thermal and electrochemical stability, and widely tunable and high tensile modulus even at relatively low polymer content. MICs show great promise as solid electrolytes for solid state batteries. This dissertation describes the preparation and characterization of MIC electrolyte membranes. These transparent, flexible, and tough membranes are prepared through a convenient solvent casting process. A large variety of ILs, including both hydrophilic and hydrophobic examples, are suitable to prepare MIC electrolyte membranes by adjusting the solvents used in the casting process. The prepared membranes show a biphasic internal structure consisting of a PBDT-rich “bundle” phase and an IL-rich “puddle” (interconnected fluid) phase. Similar to the bulk MIC ingots prepared previously through an interfacial ion exchange process, the MIC membranes also have high ionic conductivity and tensile modulus at low polymer content. A MIC membrane composed of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyr₁₄TFSI), LiTFSI, and PBDT in a mass ratio of 8:1:1 is tested as a solid electrolyte for lithium metal batteries. This electrolyte membrane shows high ionic conductivity and high rigidity. The shear storage modulus of this MIC electrolyte membrane only decreases by 35% when heated to 200 °C from room temperature, suggesting great mechanical stability at high temperatures. The electrolyte membrane is successfully used as solid electrolyte for a Li/LiFePO₄ battery working over a large temperature range from 23 to 150 °C, and the discharge capacity retention of the cell is as high as 99% after 50 cycles at 150 °C. By replacing the IL in the MIC with a charge-neutral liquid, single-ion-conducting polymer gel electrolyte composed of PBDT and polyethylene glycol (PEG) oligomer are obtained. Similar to the MICs, these single-ion-conducting materials also have high Young’s modulus and biphasic internal structures. This study reveals that the counter ion (Li⁺ or Na⁺) of the PBDT has a major effect on both the ionic conductivity and modulus of the materials. Due to the stronger intermolecular interactions, LiPBDT-PEG demonstrates lower ionic conductivity but higher Young’s modulus. This dissertation also evaluates the viability of rigid PBDT as a polymer binder for electrodes. Aqueous solution-processed LiFePO₄ electrodes with only 3 wt% PBDT demonstrate stable cycling over 1000 cycles without obvious capacity decay, and the rate capacity of these aqueous solution-processed electrodes are comparable to the electrodes prepared with conventional poly(vinylidene difluoride) (PVDF) as the binder, suggesting PBDT can serve as a potential electrode binder for commercial applications. / A solid electrolyte is a crucial component of any solid state battery. Polymer gel electrolytes have received increasing attention in recent years due to their high ionic conductivity, flexibility, and improved safety. However, a general tradeoff usually exists between the mechanical properties and ionic conductivity in such materials. Molecular ionic composites (MICs) are a new type of rigid polymer gel electrolyte based on ionic liquids (ILs) and a double helical rigid-rod polyamide, poly(2,2′-disulfonyl-4,4′-benzidine terephthalamide) (PBDT). MICs have high ionic conductivity, high thermal and electrochemical stability, and widely tunable and high tensile modulus even at relatively low polymer content. MICs show great promise as solid electrolytes for solid state batteries. This dissertation describes the preparation and characterization of MIC electrolyte membranes. These transparent, flexible, and tough membranes are prepared through a convenient solvent casting process. A large variety of ILs, including both hydrophilic and hydrophobic examples, are suitable to prepare MIC electrolyte membranes by adjusting the solvents used in the casting process. The prepared membranes show a biphasic internal structure consisting of a PBDT-rich "bundle" phase and an IL-rich "puddle" (interconnected fluid) phase. Similar to the bulk MIC ingots prepared previously through an interfacial ion exchange process, the MIC membranes also have high ionic conductivity and tensile modulus at low polymer content. A MIC membrane composed of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyr14TFSI), LiTFSI, and PBDT in a mass ratio of 8:1:1 is tested as a solid electrolyte for lithium metal batteries. This electrolyte membrane shows high ionic conductivity and high rigidity. The shear storage modulus of this MIC electrolyte membrane only decreases by 35% when heated to 200 °C from room temperature, suggesting great mechanical stability at high temperatures. The electrolyte membrane is successfully used as solid electrolyte for a Li/LiFePO4 battery working over a large temperature range from 23 to 150 °C, and the discharge capacity retention of the cell is as high as 99% after 50 cycles at 150 °C. By replacing the IL in the MIC with a charge-neutral liquid, single-ion-conducting polymer gel electrolyte composed of PBDT and polyethylene glycol (PEG) oligomer are obtained. Similar to the MICs, these single-ion-conducting materials also have high Young's modulus and biphasic internal structures. This study reveals that the counter ion (Li+ or Na+) of the PBDT has a major effect on both the ionic conductivity and modulus of the materials. Due to the stronger intermolecular interactions, LiPBDT-PEG demonstrates lower ionic conductivity but higher Young's modulus. This dissertation also evaluates the viability of rigid PBDT as a polymer binder for electrodes. Aqueous solution-processed LiFePO4 electrodes with only 3 wt% PBDT demonstrate stable cycling over 1000 cycles without obvious capacity decay, and the rate capacity of these aqueous solution-processed electrodes are comparable to the electrodes prepared with conventional poly(vinylidene difluoride) (PVDF) as the binder, suggesting PBDT can serve as a potential electrode binder for commercial applications. / Doctor of Philosophy / Solid state batteries are widely considered as the pathway to next-generation high performance batteries. In a solid state lithium battery, the liquid organic carbonate electrolyte is replaced with a solid electrolyte. Polymer gel electrolytes are a type of potential solid electrolyte that have been widely studied in recent decades. This dissertation describes the application of a rigid polymer in preparing polymer gel electrolytes. This highly charged and rigid polymer is a water-soluble polyamide known as PBDT with a double helical structure akin to DNA. Through a modified solvent casting process, a new type of polymer gel electrolyte, known as molecular ionic composite (MIC), is prepared using PBDT and various ionic liquids. Extra salt (which can contain lithium) can also be incorporated into the MIC membrane. This type of new polymer gel electrolyte is rigid with high tensile modulus even at high temperatures and low polymer (PBDT) content. MIC membranes are used as solid electrolytes for lithium metal batteries working over a wide temperature range from 23 to 150 °C. A rigid polymer gel electrolyte can also be obtained by replacing the ionic liquids in MICs with polyethylene glycol. Besides the application in preparing solid electrolytes, PBDT is also evaluated as a polymer binder for aqueous processed electrodes. Preliminary study reveals that PBDT holds great potential for a range of commercial energy storage applications.
4

Membranes conductrices ioniques pour piles à combustible / Ion conducting membranes for fuel cells

Narducci, Riccardo 15 December 2014 (has links)
Dans cette thèse, les membranes perfluorosulfoniques (PFSA) et les polymères aromatiques sulfonés (SAP) sont étudiés en vue d'une meilleure compréhension de leurs propriétés thermodynamiques, d'hydratation, mècaniques et électriques.Concernant les PFSA: 1) Préparation de membranes Nafion ayant diverses morphologies et structures (amorphe, semi-cristalline, stratifiée) et relation avec les propriétés, comme la transition vitreuse, la fusion, la conductivité protonique. 2) Divers traitements de recuit ont été appliqués et analysés par une nouvelle méthode quantitative appelé INCA (Ionomère nc analyse), utilisant aussi des agents de recuit spéciaux. Concernant les SAP: 1) Synthèse in situ de polymères réticulés et clarification du mécanisme. 2) Optimisation du degré de reticulation en vue de la meilleure conductivité protonique. 3) Obtention d'ionomères conducteurs cationiques par échange de cations du SPEEK et détermination des propriétés de ces nouveaux ionomères. / In this thesis, perfluorosulfonic acid membranes (PFSA) and sulfonated aromatic polymers (SAP) are studied to better understandtheir thermodynamic, hydration, mechanical and electrical properties. The following main points were addressed:Regarding PFSA:1) Nafion membranes with various morphology and microstructure (amorphous, semi-crystalline, layered) were prepared and the relation to the properties, such as glass and melting transitions, and proton conductivity, was established.2) Various annealing treatments were performed and analyzed by the quantitative INCA (Ionomer nc Analysis) method using also special annealing agents. Regarding SAP:1) The in situ synthesis of cross-linked polymers was studied and the mechanism was clarified. 2) The degree of cross-linking was optimized for best proton conductivity.3) Cation-conducting ionomers were obtained by cation exchange of SPEEK and the properties of these new ionomers were determined.
5

Lithium ion conducting glass-ceramics with NASICON-type structure based on the Li1+x Crx (Gey Ti1-y)2-x (PO4)3 system / Vitrocéramique conductrice au lithium-ion avec structure de type NASICON basée sur le système Li1+xCrx(GeyTi1-y)2-x(PO4)3

Nuernberg, Rafael 22 March 2018 (has links)
L'objectif principal de ce travail est de développer une nouvelle vitrocéramique structurée par NASICON avec une conductivité Li-ion élevée. Par conséquent, ce travail présente une nouvelle série de compositions de type NASICON sur la base du système Li1+xCrx(GeyTi1-y)2-x(PO4)3. Dans un premier temps, une composition spécifique de ce système a été synthétisée par la méthode de fusion et refroidissement rapide, suivie d'une cristallisation. Le comportement de cristallisation du verre précurseur a été examiné par calorimétrie différentielle à balayage et spectroscopie infrarouge. Les principaux résultats indiquent que le verre précurseur présente une nucléation homogène, a une stabilité de verre considérable et cristallise une phase de type NASICON, qui permet d'obtenir des électrolytes solides par voie vitrocéramique. Dans une deuxième étape, on examine l'effet de la substitution de Ti par Cr et Ge sur la stabilité de verre du verre précurseur, sur les paramètres structuraux de la phase cristalline NASICON et sur les propriétés électriques des vitrocéramiques. Par conséquent, un ensemble de seize compositions de ce système est synthétisé. Les principaux résultats indiquent que la stabilité de verre augmente lorsque Ti est remplacé par Ge et Cr. Après cristallisation, toutes les vitrocéramiques présentent une phase de type NASICON, et leurs paramètres de maille décroissent avec Ge et augmentent avec la teneur en Cr, ce qui permet de régler le volume de la cellule unitaire de la structure de type NASICON. De plus, la conductivité ionique et l'énergie d'activation pour la conduction du lithium dans les vitrocéramiques dépendent notamment du volume de la cellule unitaire de la structure de type NASICON. Enfin, la fenêtre de stabilité électrochimique de la vitrocéramique à structure NASICON de conductivité ionique la plus élevée est étudiée. Les mesures de voltampérométrie cyclique sont suivies par spectroscopie d'impédance électrochimique in situ, permettant de déterminer l'effet des réactions d'oxydation et de réduction sur les propriétés électriques des vitrocéramiques en question. La spectroscopie photoélectronique par rayons X, à son tour, est appliquée pour déterminer quelles espèces chimiques subissent une réduction/oxydation. Nos résultats révèlent que la stabilité électrochimique de ce matériau est limitée par la réduction des cations Ti+4 dans les faibles potentiels et par l'oxydation des anions O-2 dans les hauts potentiels. Aux hauts potentiels, un comportement similaire a également été rencontré pour d'autres conduites Li-ion de type NASICON bien connues, suggérant que le comportement électrochimique dans les potentiels oxydatifs pourrait être généralisé pour les phosphates à structure NASICON. / The primary goal of this work is to develop a new NASICON-structured glass-ceramic with high Li-ion conductivity. Therefore, this work introduces a new series of NASICON-type compositions based on the Li1+xCrx(GeyTi1-y)2-x(PO4)3 system. At first, a specific composition of this system is synthesized by the melt-quenching method, followed by crystallization. The crystallization behavior of the precursor glass is examined by differential scanning calorimetry and infrared spectroscopy. The main results indicate that the precursor glass presents homogeneous nucleation, has considerable glass stability and crystallizes a NASICON-like phase, which allows solid electrolytes to be obtained by the glass-ceramic route. As a second step, we examine the effect of substituting Ti by Cr and Ge on the glass stability of the precursor glass, on the structural parameters of NASICON-like phase and the electrical properties of the glass-ceramics. Hence, a set of sixteen compositions of this system is synthesized. The main results indicate that the glass stability increases when Ti is replaced by Ge and Cr. After crystallization, all the glass-ceramics present NASICON-like phase, and their lattice parameters decrease with Ge and increase with Cr content, making it possible to adjust the unit cell volume of the NASICON-type structure. Furthermore, the ionic conductivity and activation energy for lithium conduction in the glass-ceramics are notably dependent on the unit cell volume of the NASICON-type structure. Finally, the electrochemical stability window of the NASICON-structured glass-ceramics of highest ionic conductivity is investigated. Cyclic voltammetry measurements are followed by in situ electrochemical impedance spectroscopy, enabling the effect of oxidation and reduction reactions on the electrical properties of the glass-ceramics in question to be determined. X-ray photoelectron spectroscopy, in turn, is applied to determine which chemical species undergo reduction/oxidation. Our findings reveal that the electrochemical stability of this material is limited by the reduction of Ti+4 cations in low potentials and by the oxidation of O-2 anions in high potentials. At high potentials, similar behavior is also encountered for other well-known NASICON-like Li-ion conducting suggesting that the electrochemical behavior in oxidative potentials could be generalized for NASICON-structured phosphates.
6

Structure And Electrical Transport Studies Of Lithium Ion Conducting Glasses

Ganguli, Munia 11 1900 (has links) (PDF)
No description available.
7

Multiscale Transport and Dynamics in Ion-Dense Organic Electrolytes and Copolymer Micelles

Kidd, Bryce Edwin 23 September 2016 (has links)
Understanding molecular and ion dynamics in soft materials used for fuel cell, battery, and drug delivery vehicle applications on multiple time and length scales provides critical information for the development of next generation materials. In this dissertation, new insights into transport and kinetic processes such as diffusion coefficients, translational activation energies (Ea), and rate constants for molecular exchange, as well as how these processes depend on material chemistry and morphology are shown. This dissertation also aims to serve as a guide for material scientists wanting to expand their research capabilities via nuclear magnetic resonance (NMR) techniques. By employing variable temperature pulsed-field-gradient (PFG) NMR diffusometry, which can probe molecular transport over nm – μm length scales, I first explore transport and morphology on a series of ion-conducting materials: an organic ionic plastic crystal, a proton-exchange membrane, and a polymer-gel electrolyte. These studies show the dependencies of small molecule and ion transport on modulations to material parameters, including thermal or magnetic treatment, water content, and/or crosslink density. I discuss the fundamental significance of the length scale over which translational Ea reports on these systems (~ 1 nm) and the resulting implications for using the Arrhenius equation parameters to understand and rationally design new ion-conductors. Next, I describe how NMR spectroscopy can be utilized to investigate the effect of loading a small molecule into the core of a spherical block copolymer micelle (to mimic, e.g., drug loading) on the hydrodynamic radius (rH) and polymer chain dynamics. In particular, I present spin-lattice relaxation (T1) results that directly measure single chain exchange rate kexch between micelles and diffusion results that inform on the unimer exchange mechanism. These convenient NMR methods thus offer an economical alternative (or complement) to time-resolved small angle neutron scattering (TR-SANS). / Ph. D.
8

Application of Computer Simulation in the Investigation of Photoelectric Materials

Yang, Hsiao-ching 25 July 2004 (has links)
In this thesis, we investigated several photoelectric material systems consisted of conjugated polymers by means of computer simulation. We combined several theory and simulation methods to meodeling different subjects from atomic to mesoscopic scale. We dealt with the problems such as quantum efficiency, structure characteristic, and the phase behavior in material. We hope to have better understanding of the relationship between structure characteristic and functional property in material. It will help an engineering designer to adjust the variables that optimize characteristics linking the synthesis of advanced materials with desired physical properties. This work can be divided into three parts. Long side chain substituted PPV polymers applied in light-emitting diode material : Molecular dynamics simulations were employed to investigate structure features and segment orientation of four poly(phenylene vinylene) (PPV)-like conjugated polymers with long flexible side chains at room temperature. In the simulations, the main chains of the polymers were found to be semi-rigid and to exhibit a tendency to coil into ellipsoidal helices or form zigzag conformations of only limited regularity. It was shown that continuous segments of a chain which are quasi-coplanar along the backbone are in a range of 2~4 repeat units. This implies that long-range electron transfer along same backbones of these polymers may not happen but may be mediated by interchain interactions. The ordered orientation and coupling distance of interchain aromatic rings are found to correlate with important optical properties of materials. Then we combined molecular dynamics simulation and density matrix methods modeling of amorphous light-emitting polymers. A simplified method combining molecular dynamics (MD) simulation and density matrix (DM) theory was developed for the prediction of optical properties of long side chain substituted poly(phenylene vinylene) (PPV) polymers. This MD+DM method takes account of the complexity of molecular packing of polymer chains. The method has been tested to simulate the absorption spectra of four model systems. The wavelengths of absorption maxima of the calculated spectra of these four conjugated polymers are in reasonable agreement with experimental data. The simulation also demonstrated that the importance of including interchain interactions in the calculation. Ion-conducting polymer sPBI-PS(Li+): To understand the mechanism of ionic migration in the amorphous matrixes of polymer electrolytes is crucial for their applications in modern technologies. Here, molecular dynamics (MD) simulation was carried out to investigate the ionic conduction mechanism of a particular conjugated rigid-rod polymer, sPBI-PS(Li+). The backbone of this polymer is poly[(1, 7- dihydrobenzo[1, 2-d:4,5-d¡¦]diimidazole- 2,6-diyl)-2-(2-sulfo)-p-phenylene]. The polymer has pendants of propane sulfonate Li+ ionomer. The MD simulations showed that the main chains of sPBI-PS(Li+) are in layer-like structure. The further detailed structure analysis suggested that the £k-electron of this polymer is not delocalized among aromatic rings. This agrees with the experimental result that sPBI-PS(Li+) shows no electronic conductivity and the conductivity of this polymer is mainly ionic. The calculated migration channels of lithium ions and electrostatic potential distributions indicated clearly that the polymer matrix is anisotropic for the migrations of ions. The migration of lithium ions along the longitudinal direction is more preferable than that along the transverse direction. The relaxations of the polymer host were found to play important roles in the transfer process of lithium ions. The hopping of lithium ion from one -SO3-1 group to another is correlated strongly with characteristic motions of -SO3-1 group on a time scale of about 10-13 s. Self-assembly functional material. Dissipative particle dynamics (DPD) simulations were carried out to investigate mixed ionic and non-ionic molecules, sodium tetradecyl sulfate (STS) and tetradecyl triethoxylated ether (C14E3) aqueous system. Different types of mixed micelles are formed depending on the concentrations of STS and C14E3. Our results are in good agreement to the early NMR measurements. From the investigation of surfactant aggregation, we understand the self-assembly mechanism and classical phase behavior in general diblock copolymer. Further, we investigated the self-assembly process on a particular mushroom-shaped supramolecular film material from molecular character to phase behavior. The miniaturized rod-coil triblock copolymers (PS-PI-RCBC) HEMME had been found to self-assemble into well-ordered nanostructures and unusual head to tail multilayer structure. The purpose of our study is to obtain fundamental understanding the connection of the inherent morphological characterization of single molecule and the mechanism of phase behavior of this polar self-assembly system. Dissipative particle dynamics simulation was carried out to study the mechanism of phase behavior of the solvent-copolymers system. We found that the solvent-induced polar effect under different temperature is important in the process of self-assembly of block copolymers. In different temperature the solvent induces hybrid structure aggregation. Our results are consistent with experimental observations and give evidence for a special mechanism governing the unusual phase behavior in thin films of modulated phases. The sizes and stabilization energies of mushroom-shaped supramolecular clusters were predicted by molecular modeling method. Clusters of sizes from 16 to 90 molecules were found to be stable. In combination of classical and simple quantum mechanical calculations, the band gaps of HEMME clusters with various sizes were estimated. The band gap was converged at 2.45 eV for cluster contains 90 molecules. Nonlinear optical properties of the material were investigated by the semi-empirical quantum mechanical calculations of molecular dipole moment and hyperpolarizabilities. Significant second-order nonlinear optical properties were shown from these calculated properties.
9

Développement de méthodes accélérées pour la synthèse de polymères et réseaux conducteurs ioniques à base 1,2,3-triazolium / Development of accelerated methods for the synthesis of 1,2,3-triazolium-based ion conducting polymers and networks

Obadia, Mona 24 June 2016 (has links)
Cette thèse s'intéresse au développement de procédés monotopes (en une seule étape) permettant la synthèse accélérée de polymères conducteurs ioniques.Une étude bibliographique sur les poly(liquides ioniques) à base 1,2,3-triazolium (TPILs) a démontré leurs richesses structurale et fonctionnelle inégalées. Leur synthèse requière cependant plusieurs étapes nécessitant l'emploi de catalyseurs, de solvants et d'agents de polymérisation.Une première partie est consacrée au développement d'une voie de synthèse accélérée permettant d'accéder en une seule étape, sans solvant, ni catalyseur à des TPILs de structures variées. Il est en effet aisément possible de moduler les structures chimiques de l'espaceur, du contre-anion et du substituant en position N-3 du groupe 1,2,3-triazolium à partir d'un large choix de monomères a-azoture-?-alcyne et d'agents alkylants.Une seconde partie est consacrée à l'extension de cette voie de synthèse originale à l'élaboration d'une série de réseaux conducteurs ioniques, démontrant ainsi la souplesse du procédé et l'immense possibilité de variation structurale. Ces réseaux possèdent les propriétés uniques des matériaux vitrimères sur la base d'échanges dynamiques des points de réticulation par des réactions de transalkylation des liaisons C-N sous contrainte et température. Ils peuvent ainsi être remis en forme et recyclés sans pertes majeures de leurs propriétés et constituent donc le premier exemple de vitrimère fonctionnel. L'ensemble de ces matériaux de par leurs propriétés ainsi que leur rapidité et leur facilité de synthèse constituent donc une avancée majeure dans le domaine des polymères conducteurs ioniques et leurs applications / This PhD thesis tackles the development of monotopic (or single step) processes enabling the accelerated synthesis of ion conducting polymer materials. A bibliographic study on 1,2,3-triazolium-based poly(ionic liquid)s (TPILs) have demonstrated their unequaled structural and functional richness. However, their syntheses require several synthetic steps and the use of catalysts, solvents and polymerization mediators.A first part is devoted to the development of an accelerated synthetic approach enabling in a single step to access TPILs with broad structural variety without solvent nor catalyst. Indeed the chemical structure of the spacer, the counter-anion and the N-3 substituent of the 1,2,3-triazolium group can be readily tuned from a broad library of a-azide-?-alkyne monomers and alkylating agents.A second part is devoted to the extension of this original synthetic approach to the formation of a series of ion conducting polymer networks, thus demonstrating the flexibility of the process and the broad capacity in structural design. These networks possess the unique properties of vitrimer materials based on dynamic exchanges of the cross-linking points by transalkylation reactions of C-N bonds under strain and temperature. They can thus be reshaped and recycled without significant loss of their properties, which constitute the first example of functional vitrimer.The properties of these materials, as well as the rapidity, the versatility and the flexibility of their syntheses constitute a major breakthrough in the field of ion conducting polymer materials and their applications

Page generated in 0.102 seconds