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Estudo por ressonância magnética nuclear H e 7Li de eletrólitos poliméricos baseados em amilopectina e LiClO4 / Nuclear magnetic resonance study of the polymer electrolytes based on amilopectine and LiClO4Leandro Vinicius da Silva Lopes 18 December 2001 (has links)
Os eletrólitos poliméricos sólidos têm sido alvo de estudos devido às suas diversas aplicações em baterias e dispositivos eletrocrômicos. O material que estudamos é composto por amilopectina, um dos principais componentes do amido, polimerizado com glicerol, que forma filmes. Quando dopamos esse material com sal de lítio, LiClO4, ele se comporta como um eletrólito polimérico sólido, condutor iônico de lítio (σ ≈ 3x105 S/cm a 300K). Nesse trabalho apresentaremos o estudo desse material utilizando técnicas de Ressonância Magnética Nuclear (RMN) nos núcleos H e 7Li. Fizemos medidas da largura de linha e do tempo de relaxação spin-rede (T11) em função da temperatura (183K a 393K) com o objetivo de obter informações tanto sobre a dinâmica iônica, através da ressonância do 7Li, como sobre a dinâmica dos prótons existentes na cadeia polimérica e do plasticizante através da ressonância do 1H. Os resultados das medidas de relaxação do 7Li mostram a presença de um máximo em T1-1 a temperatura de ≈ 320k. Nosso estudo mostra que o mecanismo de relaxação dominante para o 7Li é a interação entre o momento quadrupolar do 7Li e as flutuações dos gradientes de campo elétrico produzidos pelas distribuições de carga no sítio do núcleo. A energia de ativação para o processo de difusão do lítio é Ea ≈ 0.19eV, e o tempo de correlação à temperatura ambiente é τ ≈ 1.6x10-9s, que indica uma mobilidade do lítio superior às observadas em eletrólitos poliméricos com base de PEO e com base de PEO-hidroxietilcelulose, mas comparáveis às observadas em eletrólitos poliméricos com plasticizante / Solid polymer electrolytes have been studied due to his several applications in batteries and electrochromic devices. The material studied is a thermoplastic material that was obtained from amylopectin rich starch plasticized with glycerol. When doped with lithium salt, LiClO4, this material has the property to form films and it can be used as a solid polymer electrolyte, lithium ionic conductor (σ ≈ 3x105 S/cm a 300K). In this work, we report H e 7Li. nuclear magnetic resonance (NMR) measurements as a function of temperature in a series of amylopectin films. Measurements of lineshapes and spin-lattice relaxation times (T11) as a function of temperature (183K - 393K) were used to obtain information about ionic motion (7Li resonance) and polymer chain dynamics (1H) in polymer electrolytes. The results of 7Li spin-lattice relaxation show a maximum T1-1 at around ≈ 320k. Our study shows that the 7Li dominant relaxation mechanism is the interaction between quadrupolar moment of 7Li and the fluctuations of the electric field gradient produced by the charge distributions on the nucleus site. The activation energy for the lithium diffusion process is Ea ≈ 0.19eV, and the correlation time at room temperature is τ ≈ 1.6x10-9s. That indicates a lithium mobility greater than the observed in polymer electrolytes based on PEO and on PEO-hidroxiethilcelulose, but comparable to the ones observed in solid polymer electrolyte
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Eletrólitos poliméricos géis à base de pectina / Polymer electrolytes gel based on pectinJuliana Ramos de Andrade 23 July 2010 (has links)
Esta dissertação apresenta a preparação e caracterização de eletrólitos poliméricos géis (EPGs) a partir de pectina comercial GENU®, plastificada com glicerol e dopada com perclorato de lítio. O objetivo é a utilização de uma nova matéria-prima para a obtenção de eletrólitos poliméricos substituindo os polímeros sintéticos. A pectina é um polímero natural presente nas plantas; quimicamente é um polímero heterogêneo, e estruturalmente, é constituída unidades repetidas de (1→4)-α-D-ácido galacturônico. Os eletrólitos foram preparados usando como sal LiClO4 (0,24 g ou 30 [O]/[Li]), e 0,6 g de pectina com diferentes quantidades de glicerol (0 g - 2,0 g; 0% - 70%) como plastificante. Os filmes foram caracterizados por espectroscopia de impedância, difração de raios-X, UV-Vis, FT-IR, análises térmicas (DSC e TG). Os melhores resultados foram apresentados pelos filmes constituídos com 70% de glicerol e 30 [O]/[Li] e 68% de glicerol e 0,24 g de LiClO4. .Os filmes com 68% de glicerol apresentam valores de condutividade iônica de 1,61x10-4 S.cm-1 em temperatura ambiente aumentando para 1,72x10-3 S.cm-1 à 80°C, e uma transmitância de 80% no intervalo do visível. Os valores da energia de ativação para este filme é em torno de 37 KJmol-1. Também foi verificada a estabilidade eletroquímica em uma faixa de potencial que varia entre -1,5 a +1,5V. Os filmes com 70% de glicerol apresentam os melhores valores de condutividade iônica de 3,08x10-4 S.cm-1 em temperatura ambiente para 2,94x10-3 S.cm-1 à 80°C, e energia de ativação em torno de 35 KJmol-1, e transmitância de 75% no intervalo do visível. Os resultados obtidos indicaram que os eletrólitos a base de pectina são promissores para aplicações em dispositivos opto-eletroquimicos. / This work presents the preparation and characterization of pectin GENU®-based gel polymeric electrolytes (GPEs), plasticized with glycerol and doped with lithium perchlorate. The use of a new raw material for the production of polymeric electrolytes, as substitutes of synthetic polymers is the proposal of this work. Pectin is a natural polymer found in plants. This polymer is chemically heterogeneous and structurally, are composed of a main linear chain of (1→4)-α-D-galacturonic acid. The electrolytes were prepared using salt as LiClO4 (0.24 g or 30 [O]/[Li]) to 0.6 g of pectin and with different amounts of glycerol (0-2.0g, 0-70%) as plasticizer. The films were characterized by impedance spectroscopy, X-ray diffraction, UV-Vis, FT-IR, thermal analysis (DSC and TG). The best results were obtained with films containing 70% of glycerol and 30 [O]/[Li] and 68% of glycerol and 0.24 g LiClO4. The films with 68% of glycerol exhibit ionic conductivity values of 1.61 x10-4 S.cm-1 at room temperature with increase to1.72 x10-3 S.cm-1 at 80°C, and showed a transmittance of 80% in the visible range. The values of activation energy for this sample is around 37 kJmol-1. It was also observed the electrochemical stability in the potential range of -1.5 to +1.5 V. The films with 70% of glycerol showed best ionic conductivity values of 3.08 x10-4 S.cm-1 at room temperature wich increase to 2.94 x10-3 S.cm-1 at 80°C, and activation energy around 35 kJmol-1, and a transmittance of 75% in the visible range. All the obtained results show pectin-based polymer electrolytes over promising materials to be used in opto-electrochemical devices.
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Eletrólitos sólidos poliméricos à base de polissacarídeos: síntese e caracterização. / Solid polymer electrolytes based on polysacharide: synthesis and characterization.Anelise Maria Regiani 10 November 2000 (has links)
A síntese e a caracterização de um novo tipo de eletrólito sólido polimérico são descritas neste trabalho. Os materiais preparados consistiram de filmes de hidroxietil celulose ou hidroxipropil celulose entrecruzadas com diisocianatos de poli(óxido de etileno) e poli(óxido de propileno) ou enxertadas com monoisocianato de poli(óxido de propileno). Todos estes isocianatos foram sintetizados a partir das respectivas aminas comerciais. Filmes de hidroxietil celulose entrecruzada com hexametileno diisocianato ou enxertados com fenil isocianato também foram estudados. Como técnicas de caracterização foram utilizadas espectroscopia no infravermelho, no ultravioleta e de ressonância magnética nuclear, análises térmicas e difração de raios-X. Os filmes dopados com LiClO4 foram caracterizados utilizando-se as mesmas técnicas e a condutividade foi determinada através do método de impedância complexa. Os resultados foram da ordem de 10-5 Scm-1 a 60oC. Este valor permitiu concluir que as cadeias de derivado de celulose parecem não influenciar no fenômeno de condução; aparentemente este encontra-se mais relacionado ao tipo de isocianato utilizado na formação do filme. Os resultados de condutividade e de mobilidade de cadeia polimérica indicam que os sistemas aqui estudados podem ser aplicados como eletrólitos sólidos poliméricos. Os filmes com isocianatos comerciais, no entanto não apresentaram resultado de condução interessante. / The synthesis and characterization of new types of solid polymer electrolytes based on hydroxyethyl and hydroxypropyl cellulose grafted with different polyethers were investigated. The synthesis is based on the reaction between the cellulose derivative and mono and difunctional isocyanates prepared from amines of polyethylene oxide and polypropylene oxide. It were also synthesized films of hydroxyethyl cellulose grafted with hexamethylene diisocyanate and phenylisocyanate. These materials were characterized through techniques of infrared, ultraviolet and nuclear magnetic ressonance spectroscopies, thermal analysis and X-ray diffraction. The films of polysaccharide and polyether that contained LiClO4 showed conductivity values of the order of 10-5 Scm-1 at 60oC. The value of this parameter seems to be independent of the cellulose derivative parameters and it is better related to the type of isocyanate grafted on the polysaccharide chain. The conductivity and chain mobility results show that the systems studied here can be applied as solid polymer electrolytes. The materials synthesized using commercial isocyanates as grafting reactant did not show interesting conductivity response.
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Development of solid polymer electrolytes of polyurethane and polyether-modified polysiloxane blends with lithium saltsWang, Shanshan January 2007 (has links)
No description available.
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Molecular Structure and Dynamics of Novel Polymer Electrolytes Featuring Coulombic LiquidsYu, Zhou 25 January 2019 (has links)
Polymer electrolytes are indispensable in numerous electrochemical systems. Existing polymer electrolytes rarely meet all technical demands by their applications (e.g., high ionic conductivity and good mechanical strength), and new types of polymer electrolytes continue to be developed. In this dissertation, the molecular structure and dynamics of three emerging types of polymer electrolytes featuring Coulombic liquids, i.e., polymerized ionic liquids (polyILs), nanoscale ionic materials (NIMs), and polymeric ion gels, were investigated using molecular dynamics (MD) simulations to help guide their rational design.
First, the molecular structure and dynamics of a prototypical polyILs, i.e., poly(1-butyl-3-vinylimidazolium hexafluorophosphate), supported on neutral and charged quartz substrates were investigated. It was found that the structure of the interfacial polyILs is affected by the surface charge on the substrate and deviates greatly from that in bulk. The mobile anions at the polyIL-substrate interfaces diffuse mainly by intra-chain hopping, similar to that in bulk polyILs. However, the diffusion rate of the interfacial mobile anions is much slower than that in bulk due to the slower decay of their association with neighboring polymerized cations.
Second, the structure and dynamics of polymeric canopies in the modeling NIMs where the canopy thickness is much smaller than their host nanoparticle were studied. Without added electrolyte ions, the polymeric canopies are strongly adsorbed on the solid substrate but maintain modest in-plane mobility. When electrolyte ion pairs are added, the added counter-ions exchange with the polymeric canopies adsorbed on the charged substrate. However, the number of the adsorbed electrolyte counter-ions exceeds the number of desorbed polymeric canopies, which leads to an overscreening of the substrate's charge. The desorbed polymers can rapidly exchange with the polymers grafted electrostatically on the substrate.
Finally, the molecular structure and dynamics of an ion gel consisting of PBDT polyanions and room-temperature ionic liquids (RTIL) were studied. First, a semi-coarse-grained model was developed to investigate the packing and dynamics of the ions in this ion gel. Ions in the interstitial space between polyanions exhibit distinct ordering, which suggests the formation of a long-range electrostatic network in the ion gel. The dynamics of ions slow down compared to that in bulk due to the association of the counter-ions with the polyanions' sulfonate groups. Next, the RTIL-mediated interactions between charged nanorods were studied. It was discovered that effective rod-rod interaction energy oscillates with rod-rod spacing due to the interference between the space charge near each rod as the two rods approach each other. To separate two rods initially positioned at the principal free energy minimum, a significant energy barrier (~several kBT per nanometer of the nanorod) must be overcome, which helps explain the large mechanical modulus of the PBDT ion gel reported experimentally. / Ph. D. / Polymer electrolytes are an indispensable component in numerous electrochemical devices. However, despite decades of research and development, few existing polymer electrolytes can offer the electrochemical, transport, mechanical, and thermal properties demanded by practical devices and new polymer electrolytes are continuously being developed to address this issue. In this dissertation, the molecular structure and dynamics of three emerging novel polymer electrolytes, i.e., polymerized ionic liquids (polyILs), nanoscale ionic materials (NIMs), and polymeric ion gels, are investigated to understand how their transport and mechanical properties are affected by their molecular design. The study of polyILs focused on the interfacial behavior of a prototypical polyILs supported on neutral and charged quartz substrates. It was shown that the structure and diffusion mechanism of the interfacial polyILs are sensitive to the surface charges of the substrate and can deviate strongly from that in bulk polyILs. The study of NIMs focused on how the transport properties of the dynamically grafted polymers are affected by electrolyte ion pairs. It was discovered that the contaminated ions can affect the conformation the polymeric canopies and the exchange between the “free” and “grafted” polymers. The study of polymeric ion gels focused on the molecular and mesoscopic structure of the ionic liquids in the gel and the mechanisms of ion transport in these gels. It was discovered that the ions exhibit distinct structure at the intermolecular and the interrod scales, suggesting the formation of extensive electrostatic networks in the gel. The dynamics of ions captured in simulations is qualitatively consistent with experimental observations.
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Investigations Of Poly(Ethylene Glycol)- Based Solid Polymer And Nanocomposite ElectrolytesSingh, Thokchom Joykumar 01 1900 (has links) (PDF)
No description available.
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Preparation, Characterization And Ionic Conductivity Studies On Certain Fast Ionic ConductorsBorgohain, Madhurjya Modhur 06 1900 (has links)
Fast ionic conductors, i.e. materials in which charge transport mainly occurs through the motion of ions, are an important class of materials with immense scope for industrial applications. There are different classes of fast ionic conductors e.g. polymer electrolytes, glasses, oxide ion conductors etc. and they find applications such as solid electrolytes in batteries, in fuel cells and in electro active sensors. There are mixed conducting materials as well which have both ions and electrons as conducting species that are used as electrode materials. Specifically, polymer electrolytes 1−3 have been in use in lithium polymer batteries, which have much more advantages compared to other secondary batteries. Polymer electrolyte membranes have been in use in direct methanol fuel cells (DMFC). The membranes act as proton conductors and allow the protons produced from the fuel (methanol) to pass through. Oxide ion conductors are used in high temperature solid oxide fuel cells (SOFC) and they conduct via oxygen ion vacancies. Fuel cells are rapidly replacing the internal combustion engines, because they are more energy efficient and environment friendly. The present thesis is concerned with the preparation, characterization and conductivity studies on the following fast ionic conductors: (MPEG)xLiClO4, (MPEG)xLiCF3SO3 where (MPEG) is methoxy poly(ethylene glycol), the hydrotalcite [Mg0.66Al0.33(OH)2][(CO3)0.17.mH2O] and the nanocomposite SPE, (PEG)46 LiClO4 with dispersed nanoparticles of hydrotalcite. We also present our investigations of spin probe electron spin resonance (SPESR) as a possible technique to determine the glass transition temperature (Tg) of polymer electrolytes where the conventional technique of Tg determination, namely, differential scanning calorimetry, (DSC), is not useful due to the high crystallinity of the polymers. In the following we summarize the main contents of the thesis.
In Chapter 1 we provide a brief introduction to the phenomenon of fast ionic conduction. A description of the different experimental techniques used as well as the relevant theories is also given in this chapter. In most solid polymer electrolytes (SPE), the usability is limited by the low value of the ionic conductivity. A number of different routes to enhance the electrical, thermal and mechanical properties of these materials is presently under investigation. One such route to enhance the ionic conductivity in polymer electrolytes is by irradiating the polymer electrolyte with gamma rays, electron beam, ion beams etc. In Chapter 2, we describe our work on the effect of electron beam (e-beam) irradiation on the solid polymer electrolytes (MPEG)xLiClO4 and (MPEG)xLiCF3SO3. The polymer used is methoxy poly(ethylene glycol) or poly(ethylene glycol) methyl ether with a molecular weight 2000. Salts used are LiClO4 and LiCF3SO3. ’x’ in the subscript is a measure of the salt concentration; it is the ratio of the number of ether oxygens in the polymer chain to that of the Li+ ion. ’x’ values chosen are 100, 46, 30 and 16. Nearly one order of magnitude increase in the conductivity is observed for samples (MPEG)100LiClO4 and (MPEG)16LiCF3SO3 on irradiation. It was found that the increase in the net ionic conductivity is a function of both the irradiation dose and the salt concentration. The enhanced ionic conductivity remains constant for ∼ 100 hrs, which signifies a possible near permanent change in the polymer electrolyte system due to irradiation. The samples were also characterized using DSC and Fourier transform infrared spectroscopy (FTIR). DSC results could be correlated with conductivity findings, giving low Tg values for samples having high conductivity. It was also found that there is a small increase in the crystalline fraction of the samples on irradiation, which agrees with earlier reports on samples irradiated with low dosage. FTIR results are suggestive of decreased cross linking as the reason for increased ionic conductivity. However, this aspect needs a further confirmatory look before the findings can be termed conclusive.
In Chapter 3, we describe the studies we have carried out on Li -doped hydrotalcite. We report the details of preparation and characterization of hydrotalcite as well as NMR and ionic conductivity measurements on both doped (with Li+ ions) and undoped hydrotalcite. Hydrotalcite was prepared by co-precipitation method and the composition of hydrotalcite was chosen as [Mg0.66Al0.33(OH)2][(CO3)0.17.mH2O]. Samples were prepared with salt (LiClO4) concentration 5 %, 10 %, 15 %, 20 % and 25 %. It was found that the highest ionic conductivity occurs for the sample with 20 % doping. 7Li NMR plots for all the samples clearly show an overlap of a Gaussian and a Lorentzian lineshape. The Gaussian line is because of the presence of a less mobile fraction of the 7Li+ ions and the Lorentzian line is because of the presence of a more mobile fraction of 7Li+ ions. The highest ionic conductivity was found for the salt concentration 20 % and from the room temperature 7Li NMR studies we found that for this particular concentration, the mobile fraction of the 7Li ion is also maximum. Without the salt doping, the conductivity of the sample was too small to be measured. Temperature variation of both 1H and 7Li NMR was also done, to compare the ionic conductivities from NMR.
Another method to obtain enhanced properties in polymer electrolytes is by forming ’nanocomposite’ polymer electrolytes. Nanocomposites are formed by dispersing nanoparticles of certain materials in the polymer electrolyte matrix. Till now, nanoparticles used are mostly oxides of metals, e.g. Al2O3, TiO2, MgO, SiO2 etc and clays like montmorillonite, liponite, hydrotalcite etc. Chapter 4 describes the preparation and characterization of the nanocomposite polymer electrolyte (PEG)46LiClO4 formed with hydrotalcite nanoparticles. The polymer used is PEG, poly(ethylene glycol) of molecular weight 2000, and salt used is LiClO4. The salt concentration is selected so as to give the highest ionic conductivity for the solid polymer electrolyte. Hydrotalcite belongs to a class of materials called LDH, layered double hydroxides. The composition selected is [Mg0.66Al0.33(OH)2][(CO3)0.17 .mH2O], since this is the most stable composition. These materials are easy to prepare in the nano size and are being used in a number of applications. These are characterized by the presence of layers of positively charged double hydroxides separated by layers of anions and water molecules. The water molecules give stability to the structure. Nanoparticles of hydrotalcite were prepared in the laboratory itself. XRD data of hydrotalcite confirm the crystal structure. TEM data show the particle size to be ∼ 50 nm. The polymer electrolyte (PEG)46LiClO4 was doped with these nanoparticles and the doping levels are 1.8 %, 2.1 %, 2.7 %, 3.6 % and 4.5 % by weight. Impedance spectroscopy was used to find the ionic conductivity. We have found that the sample with a doping of 3.6 % by weight gives the highest ionic conductivity and the increase in ionic conductivity is nearly one order of magnitude. DSC was used for thermal characterization of these nanocomposites. The glass transition temperatures, Tg , found from DSC measurements corroborates the ionic conductivity data, giving the lowest Tg for the sample with highest conductivity. Temperature variation of the ionic conductivity shows Arrhenius behavior. 7Li NMR was done on the pristine SPE (PEG)46LiClO4 and the nanocomposite of (PEG)46LiClO4 with 3.6 % filler. The ionic conductivity was also estimated from the temperature variation of 7Li NMR line widths. Studies on the DSC endotherms of the nanocomposites give the fractional crystallinity of the samples. From these studies it can be concluded that the variation in ionic conductivity can be attributed to the change in fractional crystallinity; the nanocomposite polymer electrolyte having highest ionic conductivity, i.e. the NCPE with filler concentration of 3.6 % also has the lowest fractional crystallinity. Additionally, a possible increase in the segmental motion inferred from a reduction in the glass transition temperature coupled with a lowering of the activation energy may also contribute to the increased ionic conductivity in the nanocomposite polymer electrolyte.
Glass transition temperature Tg has a very important role in studying the dynamics of polymer electrolytes. In Chapter 5, we explore the possibility of using spin probe electron spin resonance (SPESR) as a tool to study the glass transition temperature of polymer electrolytes. When the temperature of the polymer is increased across the glass transition, the viscosity of the sample decreases. This corresponds to a transition from a slow tumbling regime with τc = 10−6 s to a fast tumbling regime with τc = 10−9 s where τc is the correlation time for the probe dynamics. Spin probe ESR can be used to probe this transition in polymers. We have used 4-hydroxy tempo (TEMPOL) as the spin probe which is dispersed in the nanocomposite polymer electrolyte based on (PEG)46LiClO4 and hydrotalcite. Below and across the glass transition, this nitroxide probe exhibits a powder pattern showing both Zeeman (g) and hyperfine (hf) interaction anisotropy. When the frequency of the dynamics increases such that the jump frequency f is of the same order of magnitude as the anisotropy of the hf interaction, i.e., ∼ 108 Hz, the anisotropy of the interactions averages out and a spectrum of reduced splitting and increased symmetry in the line shape is observed. This splitting corresponds to the nonvanishing isotropic value of the hyperfine tensor and is observed at a temperature higher than but correlated with Tg. The crossover from the anisotropic to isotropic spectrum is reflected in a sharp reduction in the separation between the two outermost components of the ESR spectrum, which corresponds to twice the value of the z-principal component of the nitrogen hyperfine tensor, 2Azz, from ∼75 G to ∼ 35 G. In our study, we have varied the concentration of the nano-fillers. The Tg for all the samples were estimated from the measurement of T50G and the known correlation between 4 T50G and Tg, where T50G is the temperature at which the extrema separation (2Azz) of the ESR spectra becomes 50 Gauss. The values obtained from this method are compared with the values found from DSC done on the same samples. Within experimental error, these two techniques give reasonably close values. Tg’s were also estimated by a cross over in the correlation time (τc) vs temperature plot. The τc values were calculated using a spectral simulation program. We conclude that spin probe ESR can be an alternative to the DSC technique for polymers with high fraction of crystallinity, for which DSC often does not give any glass transition signature.
In Appendix I, ionic conductivity studies on quenched and gamma irradiated polymer electrolytes (PEG)46LiClO4 and (MPEG)16LiClO4 is done. It is observed that, (i) the samples quenched to 77 K after melting show enhancement of ionic conductivity by a factor of 3 & 4; (ii) on irradiation, the ionic conductivity decreases for a dose of 5 kGy and subsequently, keeps on increasing for higher doses of 10 kGy and 15 kGy.
In Appendix II, the BASIC language program (eq-res.bas) used for impedance data analysis is given.
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Sol-Gel Derived Ionically Conducting Composites : Preparation, Characterization And Electrochemical Capacitor StudiesMitra, Sagar 02 1900 (has links) (PDF)
No description available.
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Optimization Of The Melt-Transetherification Polycondensation Route To Polyethers And Its Utilization For The Study Of Hyperbranched PolymersBehera, Girish Chandra 12 1900 (has links) (PDF)
No description available.
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Crystalline polymer and small molecule electrolytesAinsworth, David A. January 2010 (has links)
The research presented in this thesis includes a detailed investigation into factors influencing ionic conductivity in the crystalline polymer electrolyte PEO₆:LiPF₆. It has previously been shown that preparing PEO₆:LiPF₆ with PEO modified with larger –OC₂H₅ end groups increases ionic conductivity by one order of magnitude [¹],primarily due to disruption of the crystal structure caused by the inclusion of the larger end groups. In this study it is shown that by reducing PEO molecular weight in crystalline PEO₆:LiPF₆ ionic conductivity is also increased. This was attributed to an increasing concentration of polymer chain end regions upon lowering molecular weight resulting in the creation of more defects, as well as possible increases in crystallite size resulting in longer continuous pathways for ion transport. Similar results were observed using both polydispersed and monodispersed PEO to prepare complexes. In addition, it is demonstrated here that ionic conductivity in crystalline polymerelectrolytes is not confined to PEO₆:LiXF₆ (X=P, As, Sb)[²][³] type materials. The structures and ionic conductivity data are reported for a series of new crystalline polymer complexes: the alkali metal electrolytes. They are composed of low molecular weight PEO and different alkali metal hexafluoro salts (Na⁺, K⁺ and Rb⁺), and include the best conductor poly(ethylene oxide)₈:NaAsF₆ discovered to date [⁴], with a conductivity 1.5 orders of magnitude higher than poly(ethylene oxide)₆:LiAsF₆. A new class of solid ion conductor is reported: the crystalline small-molecule electrolytes. Such materials consist of lithium salts dissolved in low molecular weight glyme molecules [CH₃O(CH₂CH₂O)[subscript(n)]CH₃, n=1-12], forming crystalline complexes [⁵][⁶]. These materials are soft solids unlike ceramic electrolytes and unlike polymer electrolytes they are highly crystalline, are of low molecular weight and have no polydispersity. By varying the number of repeat units in the glyme molecule, many complexes may be prepared with a wide variety of structures. Here, ionic conductivity and cation transference number (t₊) data for several such complexes is presented [⁷][⁸][⁹].These complexes have appreciable ionic conductivities for crystalline complexes and their t₊ values vary markedly depending on the glyme molecule utilized. The differences in t₊ values can be directly attributed to differences in their crystal structures. [¹] Staunton, E., Andreev, Y.G. & Bruce, P.G. Factors influencing the conductivity of crystalline polymer electrolytes. Faraday Discussions 134, 143-156 (2007). [²] Gadjourova, Z., Andreev, Y.G., Tunstall, D.P. & Bruce, P.G. Ionic conductivity in crystalline polymer electrolytes. Nature 412, 6846 (2001). [³] Stoeva, Z., Martin-Litas, I., Staunton, I., Andreev, Y.G. & Bruce, B.G. Ionic Conductivity in the Crystalline Polymer Electrolytes PEO₆:LiXF₆, X = P, As, Sb. J. Am. Chem. Soc. 125, 4619-4626(2003). [⁴] Zhang, C., Gamble, S., Ainsworth, D., Slawin, A.M.Z., Andreev, Y.G. & Bruce, P.G. Alkali metal crystalline polymer electrolytes. Nature Materials 8, 580-584 (2009). [⁵] Henderson, W.A., Brooks, N.R., Brennessel, W.W. & Young Jr, V.G. Triglyme-Li⁺ Cation Solvate Structures: Models for Amorphous Concentrated Liquid and Polymer Electrolytes (I). Chem. Mater. 15, 4679-4684 (2003). [⁶] Henderson, W.A., Brooks, N.R. & Young Jr, V.G. Tetraglyme-Li⁺ Cation Solvate Structures: Models for Amorphous Concentrated Liquid and Polymer Electrolytes (II). Chem. Mater. 15, 4685-4690 (2003). [⁷] Zhang, C., Andreev, Y.G. & Bruce, P.G. Crystalline small-molecule electrolytes. Angewandte Chemie, International Edition 46, 2848-2850 (2007). [⁸] Zhang, C., Ainsworth, D., Andreev, Y.G. & Bruce, P.G. Ionic Conductivity in the Solid Glyme Complexes [CH₃O(CH₂CH₂O)[subscript(n)]CH₃]:LiAsF₆ (n = 3,4). J. Am. Chem. Soc. 129, 8700- 8701 (2007). [⁹] Zhang, C., Lilley, S.J., Ainsworth, D., Staunton, E., Andreev, Y.G., Slawin, A.M.Z. & Bruce, P.G. Structure and Conductivity of Small-Molecule Electrolytes [CH₃O(CH₂CH₂O)[subscript(n)]CH₃]:LiAsF₆ (n = 8-12). Chem. Mater. 20, 4039-4044 (2008).
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