The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Dong Won Kim - One of the best experts on this subject based on the ideXlab platform.
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The role of an adhesive gel-Forming Polymer coated on separator for rechargeable lithium metal Polymer cells
Solid State Ionics, 2005Co-Authors: Yeon Bok Jeong, Dong Won KimAbstract:The gel-Forming Polymer of different thicknesses was coated on both sides of polyethylene separator. The porous Polymer coated on the separator was gelled by soaking in an electrolyte solution and encapsulated a larger amount of electrolyte solution. Adhesive gel formed on both sides of PE separator provided an efficient transport of lithium ion through the solid electrolyte interphase, and the electrolyte solution absorbed in the separator gave an acceptable ionic conductivity. By using the separators with adhesive gel layer, lithium metal Polymer cells composed of a lithium anode and LiCoO2 cathode were assembled and their cycling performances were evaluated. The effect of thickness of gel Polymer layer on cycling performances of the rechargeable lithium-metal Polymer cells was investigated. ?? 2004 Published by Elsevier B.V.
Yeon Bok Jeong - One of the best experts on this subject based on the ideXlab platform.
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The role of an adhesive gel-Forming Polymer coated on separator for rechargeable lithium metal Polymer cells
Solid State Ionics, 2005Co-Authors: Yeon Bok JeongAbstract:Abstract The gel-Forming Polymer of different thicknesses was coated on both sides of polyethylene separator. The porous Polymer coated on the separator was gelled by soaking in an electrolyte solution and encapsulated a larger amount of electrolyte solution. Adhesive gel formed on both sides of PE separator provided an efficient transport of lithium ion through the solid electrolyte interphase, and the electrolyte solution absorbed in the separator gave an acceptable ionic conductivity. By using the separators with adhesive gel layer, lithium metal Polymer cells composed of a lithium anode and LiCoO 2 cathode were assembled and their cycling performances were evaluated. The effect of thickness of gel Polymer layer on cycling performances of the rechargeable lithium-metal Polymer cells was investigated.
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The role of an adhesive gel-Forming Polymer coated on separator for rechargeable lithium metal Polymer cells
Solid State Ionics, 2005Co-Authors: Yeon Bok Jeong, Dong Won KimAbstract:The gel-Forming Polymer of different thicknesses was coated on both sides of polyethylene separator. The porous Polymer coated on the separator was gelled by soaking in an electrolyte solution and encapsulated a larger amount of electrolyte solution. Adhesive gel formed on both sides of PE separator provided an efficient transport of lithium ion through the solid electrolyte interphase, and the electrolyte solution absorbed in the separator gave an acceptable ionic conductivity. By using the separators with adhesive gel layer, lithium metal Polymer cells composed of a lithium anode and LiCoO2 cathode were assembled and their cycling performances were evaluated. The effect of thickness of gel Polymer layer on cycling performances of the rechargeable lithium-metal Polymer cells was investigated. ?? 2004 Published by Elsevier B.V.
Philippe Bouillot - One of the best experts on this subject based on the ideXlab platform.
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oil core Polymer shell microcapsules by internal phase separation from emulsion droplets ii controlling the release profile of active molecules
Langmuir, 2005Co-Authors: Peter J Dowding, Rob Atkin, Brian Vincent, Philippe BouillotAbstract:Microcapsules with oil cores and solid Polymer shells have been prepared by precipitation of the Polymer from the internal phase of an oil-in-water emulsion. The dispersed phase consists of a Polymer, a good solvent for the Polymer (dichloromethane), and a poor solvent for the Polymer (hexadecane). Removal of the good solvent results in phase separation of the Polymer within the emulsion droplet, leading to the formation of a Polymeric shell surrounding the poor solvent. A UV-active organic molecule is added to the oil phase prior to emulsification. Provided this molecule has some water solubility, the release profile of the molecule from the capsule can be determined. While the microcapsule size was kept approximately constant, the influence of a wide range of factors on the release profile has been studied. These include the type and molecular weight of the shell-Forming Polymer, the molecular weight of the active ingredient molecule, the shell thickness, the use of coPolymers or Polymer blends to form ...
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oil core Polymer shell microcapsules prepared by internal phase separation from emulsion droplets i characterization and release rates for microcapsules with polystyrene shells
Langmuir, 2004Co-Authors: Peter J Dowding, Rob Atkin, Brian Vincent, Philippe BouillotAbstract:Microcapsules with an oil core surrounded by a Polymeric shell have been prepared by the controlled phase separation of Polymer dissolved within the oil droplets of an oil-in-water emulsion. The dispersed oil phase consists of the shell Polymer (polystyrene), a good solvent for the Polymer (dichloromethane), and a poor solvent for the Polymer (typically hexadecane). Removal of the good solvent results in phase separation of the Polymer within the oil droplets. If the three interfacial tensions between the core oil, the shell-Forming Polymer, and the continuous phase are of the required relative magnitudes, a Polymer shell forms surrounding the poor solvent. A UV-responsive organic molecule was added to the oil phase, prior to emulsification, to investigate the release of a model active ingredient from the microcapsules. This molecule should be soluble in the organic core but also have some water solubility to provide a driving force for release into the continuous aqueous phase. As the release rate of the...
Jack F. Douglas - One of the best experts on this subject based on the ideXlab platform.
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Stringlike Cooperative Motion Explains the Influence of Pressure on Relaxation in a Model Glass-Forming Polymer Melt
ACS Macro Letters, 2016Co-Authors: Wen-sheng Xu, Jack F. Douglas, Karl F. FreedAbstract:Numerous experiments reveal that the dynamics of glass-Forming Polymer melts are profoundly influenced by the application of pressure, but a fundamental microscopic understanding of these observations remains incomplete. We explore the structural relaxation of a model glass-Forming Polymer melt over a wide range of pressures (P) by molecular dynamics simulation. In accord with experiments for nonassociating Polymer melts and the generalized entropy theory, we find that the P dependence of the structural relaxation time (τα) can be described by a pressure analog of the Vogel–Fulcher–Tammann equation and that the characteristic temperatures of glass formation increase with P, while the fragility decreases with P. Further, we demonstrate that τα for various P can quantitatively be described by the string model of glass formation, where the enthalpy and entropy of activation are found to be proportional, an effect that is expected to apply to Polymeric materials under various applied fields.
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quantitative relations between cooperative motion emergent elasticity and free volume in model glass Forming Polymer materials
Proceedings of the National Academy of Sciences of the United States of America, 2015Co-Authors: Francis W Starr, Beatriz Pazmino A Betancourt, Paul Z Hanakata, Jack F. DouglasAbstract:The study of glass formation is largely framed by semiempirical models that emphasize the importance of progressively growing cooperative motion accompanying the drop in fluid configurational entropy, emergent elasticity, or the vanishing of accessible free volume available for molecular motion in cooled liquids. We investigate the extent to which these descriptions are related through computations on a model coarse-grained Polymer melt, with and without nanoparticle additives, and for supported Polymer films with smooth or rough surfaces, allowing for substantial variation of the glass transition temperature and the fragility of glass formation. We find quantitative relations between emergent elasticity, the average local volume accessible for particle motion, and the growth of collective motion in cooled liquids. Surprisingly, we find that each of these models of glass formation can equally well describe the relaxation data for all of the systems that we simulate. In this way, we uncover some unity in our understanding of glass-Forming materials from perspectives formerly considered as distinct.
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the meaning of the universal wlf parameters of glass Forming Polymer liquids
Journal of Chemical Physics, 2015Co-Authors: Jacek Dudowicz, Jack F. Douglas, Karl F. FreedAbstract:Although the Williams-Landell-Ferry (WLF) equation for the segmental relaxation time τ(T) of glass-Forming materials is one of the most commonly encountered relations in Polymer physics, its molecular basis is not well understood. The WLF equation is often claimed to be equivalent to the Vogel-Fulcher-Tammann (VFT) equation, even though the WLF expression for τ(T) contains no explicit dependence on the fragility parameter D of the VFT equation, while the VFT equation lacks any explicit reference to the glass transition temperature Tg, the traditionally chosen reference temperature in the WLF equation. The observed approximate universality of the WLF parameters C1(g) and C2(g) implies that τ(T) depends only on T–Tg, a conclusion that seems difficult to reconcile with the VFT equation where the fragility parameter D largely governs the magnitude of τ(T). The current paper addresses these apparent inconsistencies by first evaluating the macroscopic WLF parameters C1(g) and C2(g) from the generalized entropy ...
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fragility and cooperative motion in a glass Forming Polymer nanoparticle composite
Soft Matter, 2013Co-Authors: Beatriz Pazmino A Betancourt, Jack F. Douglas, Francis W StarrAbstract:Polymer–nanoparticle composites play a vital role in ongoing materials development. The behavior of the glass transition of these materials is important for their processing and applications, and also represents a problem of fundamental physical interest. Changes of the Polymer glass transition temperature Tg due to nanoparticles have been fairly well catalogued, but the breadth of the transition and how rapidly transport properties vary with temperature T – termed the fragility m of glass-formation – is comparatively poorly understood. In the present work, we calculate both Tg and m of a model Polymer nanocomposite by molecular dynamics simulations. We systematically consider how Tg and m vary both for the material as a whole, as well as locally, for a range of nanoparticle (NP) concentrations and for representative attractive and repulsive Polymer–NP interactions. We find large positive and negative changes in Tg and m that can be interpreted in terms of the Adam–Gibbs model of glass-formation, where the scale of the cooperative motion is identified with the scale of string-like cooperative motion. These results provide a molecular perspective of fragility changes due to the addition of NPs and for the physical origin of fragility more generally. We also contrast the behavior along isobaric and isochoric approaches to Tg, since these differing paths can be important to compare with experiments (isobaric) and simulations (very often isochoric). Our findings have practical implications for understanding the properties of nanocomposites and have fundamental significance for understanding the properties glass-Forming materials more broadly.
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antiplasticization and the elastic properties of glass Forming Polymer liquids
Soft Matter, 2010Co-Authors: Robert A Riggleman, Jack F. Douglas, Juan J De PabloAbstract:We investigate the effect of antiplasticizer additives on long-wavelength thermodynamic properties relating to the efficiency of molecular packing (density ρ and isothermal compressibility κT) and material stiffness (bulk modulus K, shear modulus G, and Poisson ratio ν) of model glass-Forming Polymer melts. Variations in the stiffness (G and molecular force constant km from the Debye–Waller factor 〈u2〉) and density ρ at a molecular scale are also considered. We find that antiplasticizer additives cause significant changes in the long-wavelength properties that are associated with an enhanced packing efficiency in the glass state, such as a decrease in κT and an increase in K, G, and ν. Moreover, values of the local elastic moduli in the glass state follow a nearly universal (approximately log-normal) distribution and a Fourier transform of the elastic constant fluctuations in space reveals a general −2 wave vector q scaling, as in order parameter fluctuations in critical fluids and magnetic systems near their critical point for phase separation and ordering, respectively. No discernible large-scale fluctuations in the density were observed, however, indicating that the local elastic constant fluctuations do not reflect density (free volume) fluctuations, as often assumed. These observations provide essential insights into how varying the fragility of glass formation, through the addition of antiplasticizer additives, alters the local mechanical properties of Polymer melts and other glass-Forming liquids.
Peter J Dowding - One of the best experts on this subject based on the ideXlab platform.
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oil core Polymer shell microcapsules by internal phase separation from emulsion droplets ii controlling the release profile of active molecules
Langmuir, 2005Co-Authors: Peter J Dowding, Rob Atkin, Brian Vincent, Philippe BouillotAbstract:Microcapsules with oil cores and solid Polymer shells have been prepared by precipitation of the Polymer from the internal phase of an oil-in-water emulsion. The dispersed phase consists of a Polymer, a good solvent for the Polymer (dichloromethane), and a poor solvent for the Polymer (hexadecane). Removal of the good solvent results in phase separation of the Polymer within the emulsion droplet, leading to the formation of a Polymeric shell surrounding the poor solvent. A UV-active organic molecule is added to the oil phase prior to emulsification. Provided this molecule has some water solubility, the release profile of the molecule from the capsule can be determined. While the microcapsule size was kept approximately constant, the influence of a wide range of factors on the release profile has been studied. These include the type and molecular weight of the shell-Forming Polymer, the molecular weight of the active ingredient molecule, the shell thickness, the use of coPolymers or Polymer blends to form ...
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oil core Polymer shell microcapsules prepared by internal phase separation from emulsion droplets i characterization and release rates for microcapsules with polystyrene shells
Langmuir, 2004Co-Authors: Peter J Dowding, Rob Atkin, Brian Vincent, Philippe BouillotAbstract:Microcapsules with an oil core surrounded by a Polymeric shell have been prepared by the controlled phase separation of Polymer dissolved within the oil droplets of an oil-in-water emulsion. The dispersed oil phase consists of the shell Polymer (polystyrene), a good solvent for the Polymer (dichloromethane), and a poor solvent for the Polymer (typically hexadecane). Removal of the good solvent results in phase separation of the Polymer within the oil droplets. If the three interfacial tensions between the core oil, the shell-Forming Polymer, and the continuous phase are of the required relative magnitudes, a Polymer shell forms surrounding the poor solvent. A UV-responsive organic molecule was added to the oil phase, prior to emulsification, to investigate the release of a model active ingredient from the microcapsules. This molecule should be soluble in the organic core but also have some water solubility to provide a driving force for release into the continuous aqueous phase. As the release rate of the...