The Experts below are selected from a list of 36000 Experts worldwide ranked by ideXlab platform
Sheng Shen - One of the best experts on this subject based on the ideXlab platform.
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Crystalline Polymer nanofibers with ultra high strength and thermal conductivity
Nature Communications, 2018Co-Authors: Ramesh Shrestha, Bikramjit Chatterjee, Teng Zheng, Zeyu Liu, Tengfei Luo, Sukwon Choi, Kedar Hippalgaonkar, Maarten P De Boer, Sheng ShenAbstract:Polymers are widely used in daily life, but exhibit low strength and low thermal conductivity as compared to most structural materials. In this work, we develop Crystalline Polymer nanofibers that exhibit a superb combination of ultra-high strength (11 GPa) and thermal conductivity, exceeding any existing soft materials. Specifically, we demonstrate unique low-dimensionality phonon physics for thermal transport in the nanofibers by measuring their thermal conductivity in a broad temperature range from 20 to 320 K, where the thermal conductivity increases with increasing temperature following an unusual ~T1 trend below 100 K and eventually peaks around 130-150 K reaching a metal-like value of 90 W m-1 K-1, and then decays as 1/T. The Polymer nanofibers are purely electrically insulating and bio-compatible. Combined with their remarkable lightweight-thermal-mechanical concurrent functionality, unique applications in electronics and biology emerge.
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Crystalline Polymer nanofibers with ultra-high strength and thermal conductivity
Nature Communications, 2018Co-Authors: Ramesh Shrestha, Bikramjit Chatterjee, Teng Zheng, Zeyu Liu, Tengfei Luo, Sukwon Choi, Kedar Hippalgaonkar, Maarten P De Boer, Sheng ShenAbstract:Polymers are widely used in daily life, but exhibit low strength and low thermal conductivity as compared to most structural materials. In this work, we develop Crystalline Polymer nanofibers that exhibit a superb combination of ultra-high strength (11 GPa) and thermal conductivity, exceeding any existing soft materials. Specifically, we demonstrate unique low-dimensionality phonon physics for thermal transport in the nanofibers by measuring their thermal conductivity in a broad temperature range from 20 to 320 K, where the thermal conductivity increases with increasing temperature following an unusual ~ T ^1 trend below 100 K and eventually peaks around 130–150 K reaching a metal-like value of 90 W m^−1 K^−1, and then decays as 1/ T . The Polymer nanofibers are purely electrically insulating and bio-compatible. Combined with their remarkable lightweight-thermal-mechanical concurrent functionality, unique applications in electronics and biology emerge. Polymers compared to structural materials usually have low strength and thermal conductivity. Here the authors show a fabrication method to form bio-compatible Crystalline polyethylene nanofibers that exhibit ultra-high strength, thermal conductivity and electrical insulation.
Ramesh Shrestha - One of the best experts on this subject based on the ideXlab platform.
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Crystalline Polymer nanofibers with ultra high strength and thermal conductivity
Nature Communications, 2018Co-Authors: Ramesh Shrestha, Bikramjit Chatterjee, Teng Zheng, Zeyu Liu, Tengfei Luo, Sukwon Choi, Kedar Hippalgaonkar, Maarten P De Boer, Sheng ShenAbstract:Polymers are widely used in daily life, but exhibit low strength and low thermal conductivity as compared to most structural materials. In this work, we develop Crystalline Polymer nanofibers that exhibit a superb combination of ultra-high strength (11 GPa) and thermal conductivity, exceeding any existing soft materials. Specifically, we demonstrate unique low-dimensionality phonon physics for thermal transport in the nanofibers by measuring their thermal conductivity in a broad temperature range from 20 to 320 K, where the thermal conductivity increases with increasing temperature following an unusual ~T1 trend below 100 K and eventually peaks around 130-150 K reaching a metal-like value of 90 W m-1 K-1, and then decays as 1/T. The Polymer nanofibers are purely electrically insulating and bio-compatible. Combined with their remarkable lightweight-thermal-mechanical concurrent functionality, unique applications in electronics and biology emerge.
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Crystalline Polymer nanofibers with ultra-high strength and thermal conductivity
Nature Communications, 2018Co-Authors: Ramesh Shrestha, Bikramjit Chatterjee, Teng Zheng, Zeyu Liu, Tengfei Luo, Sukwon Choi, Kedar Hippalgaonkar, Maarten P De Boer, Sheng ShenAbstract:Polymers are widely used in daily life, but exhibit low strength and low thermal conductivity as compared to most structural materials. In this work, we develop Crystalline Polymer nanofibers that exhibit a superb combination of ultra-high strength (11 GPa) and thermal conductivity, exceeding any existing soft materials. Specifically, we demonstrate unique low-dimensionality phonon physics for thermal transport in the nanofibers by measuring their thermal conductivity in a broad temperature range from 20 to 320 K, where the thermal conductivity increases with increasing temperature following an unusual ~ T ^1 trend below 100 K and eventually peaks around 130–150 K reaching a metal-like value of 90 W m^−1 K^−1, and then decays as 1/ T . The Polymer nanofibers are purely electrically insulating and bio-compatible. Combined with their remarkable lightweight-thermal-mechanical concurrent functionality, unique applications in electronics and biology emerge. Polymers compared to structural materials usually have low strength and thermal conductivity. Here the authors show a fabrication method to form bio-compatible Crystalline polyethylene nanofibers that exhibit ultra-high strength, thermal conductivity and electrical insulation.
Chang Dae Han - One of the best experts on this subject based on the ideXlab platform.
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Dispersion Characteristics and Rheology of Organoclay Nanocomposites Based on a Segmented Main-Chain Liquid-Crystalline Polymer Having Pendent Pyridyl Group
Macromolecules, 2006Co-Authors: Huang Wenyi, Chang Dae HanAbstract:The dispersion characteristics and rheology of organoclay nanocomposites based on a thermotropic liquid-Crystalline Polymer (TLCP) having pendent functional group were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM), and oscillatory shear rheometry. For the study, a segmented main-chain TLCP having pendent pyridyl group (PyHQ12) was synthesized and, for comparison, another segmented main-chain TLCP having pendent phenylsulfonyl group (PSHQ12) was synthesized, both TLCPs having the identical chemical structure for the main-chain backbone. The differences in phase transition temperature and rheological behavior observed between PyHQ12 and PSHQ12 are explained in terms of the self-associating characteristics of the pendent pyridyl group in PyHQ12. PyHQ12 and PSHQ12 were used to prepare nanocomposites with two commercial organoclays: one (Cloisite 30B) was natural clay (montmorillonite) treated with a surfactant (MT2EtOH) having hydroxyl groups, and the other (Cloisite 20A)...
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Rheology of Nematic Side-Chain Liquid-Crystalline Polymer: Comparison with Main-Chain Liquid-Crystalline Polymer
Macromolecules, 2002Co-Authors: Kyung Min Lee, Chang Dae HanAbstract:A nematic side-chain liquid-Crystalline Polymer (SCLCP) was synthesized by grafting a liquid-Crystalline monomer, 6-[(4-cyano-4‘-biphenyl)oxy]hexanoic acid (5CN-COOH), onto a nearly monodisperse hydroxylated polyisoprene. The linear dynamic viscoelasticity, steady shear flow, transient and intermittent shear flows, and stress relaxation of the SCLCP in the nematic state were investigated. For comparison, the rheological behavior of a main-chain liquid-Crystalline Polymer (MCLCP) was also investigated. Similarities and dissimilarities in the rheological behavior between the SCLCP and MCLCP are presented. Some of the important similarities observed are as follows. Upon start-up of shear flow, both SCLCP and MCLCP exhibited a very large overshoot peak of first normal stress difference (N1+ ) and shear stress (σ+ ). The values of first normal stress difference in steady shear flow were positive in both SCLCP and MCLCP over the entire range of shear rates tested. Some of the important dissimilarities observed ...
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Transient rheological behavior of a thermotropic liquid‐Crystalline Polymer. III. Step strain experiment and shear stress relaxation modulus
Journal of Rheology, 1994Co-Authors: Chang Dae Han, Seung Su KimAbstract:Shear stress relaxation modulus Gs(t,γ) was determined for a well‐characterized thermotropic liquid‐Crystalline Polymer, poly[(phenylsulfonyl)‐p‐phenylene 1,10‐decamethylene‐ bis(4‐oxybenzoate)] (PSHQ10) by conducting step strain experiments for a range of shear strains (γ). A fresh specimen was employed for each step strain experiment. We found that while time‐strain factorability [i.e., Gs(t,γ)=G(t)h(γ), where G(t) is the memory function and h(γ) is the damping function] was applicable to the isotropic region, it was not to the nematic region of PSHQ10. We further found that preshearing of a specimen decreased the magnitude of Gs(t,γ) considerably, suggesting that variations in the morphological state (i.e., domain texture) took place during shearing. The failure of time‐strain factorability for the PSHQ10 in the nematic region is believed to be attributable to variations in its morphology as affected by the level of applied shear strains.
Peter G Bruce - One of the best experts on this subject based on the ideXlab platform.
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factors influencing the conductivity of Crystalline Polymer electrolytes
Faraday Discussions, 2007Co-Authors: Edward Staunton, Yuri G Andreev, Peter G BruceAbstract:Crystalline Polymer electrolytes conduct, in contrast to the established view for 30 years. The Crystalline Polymer poly(ethylene oxide)6:LiXF6, X = P, As, Sb is composed of tunnels formed from pairs of (CH2–CH2–O)n chains, within which the Li+ ions reside and along which they may migrate. The anions are located outside the tunnels. PEO6:LiXF6 formed from PEO of average molecular weight 1000 Da has an average chain length of 40 A compared with a typical crystallite size of 2500 A, hence low molecular weight materials have many chain ends within a crystallite. More chain ends increase conductivity. Materials composed of polydispersed PEO (chains of different lengths) of average molecular weight 1000 Da exhibit a conductivity one order of magnitude greater than monodispersed materials of the same molecular weight. Replacing the –OCH3 groups on the chain ends with –OC2H5 increases the conductivity by a further order of magnitude. Conductivity may also be increased by isovalent or aliovalent doping of the 6 : 1 complexes in which XF−6 is replaced by N(SO2CF3)−2 or SiF2−6, respectively.
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increasing the conductivity of Crystalline Polymer electrolytes
Nature, 2005Co-Authors: Alasdair M Christie, Edward Staunton, Yuri G Andreev, Scott J Lilley, Peter G BruceAbstract:Polymer electrolytes consist of salts dissolved in Polymers (for example, polyethylene oxide, PEO), and represent a unique class of solid coordination compounds. They have potential applications in a diverse range of all-solid-state devices, such as rechargeable lithium batteries, flexible electrochromic displays and smart windows1,2,3,4,5. For 30 years, attention was focused on amorphous Polymer electrolytes in the belief that Crystalline Polymer:salt complexes were insulators. This view has been overturned recently by demonstrating ionic conductivity in the Crystalline complexes PEO6:LiXF6 (X = P, As, Sb); however, the conductivities were relatively low6,7. Here we demonstrate an increase of 1.5 orders of magnitude in the conductivity of these materials by replacing a small proportion of the XF6- anions in the crystal structure with isovalent N(SO2CF3)2- ions. We suggest that the larger and more irregularly shaped anions disrupt the potential around the Li+ ions, thus enhancing the ionic conductivity in a manner somewhat analogous to the AgBr1-xIx ionic conductors8. The demonstration that doping strategies can enhance the conductivity of Crystalline Polymer electrolytes represents a significant advance towards the technological exploitation of such materials.
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ionic conductivity in the Crystalline Polymer electrolytes peo6 lixf6 x p as sb
Journal of the American Chemical Society, 2003Co-Authors: Zlatka Stoeva, Edward Staunton, Yuri G Andreev, Isabelle Martinlitas, Peter G BruceAbstract:Ionically conducting Polymers (salts dissolved in a Polymer matrix) are of great interest because they uniquely exhibit ionic conductivity in a soft but solid membrane. As such, they are critical to the development of devices such as all-solid-state lithium batteries. The established view of ionic conductivity in Polymer electrolytes is that this occurs in amorphous materials above their glass transition temperature and that Crystalline Polymer electrolytes are insulators. In contrast, we show that three Crystalline Polymer electrolytes, poly(ethylene oxide)6:LiXF6, X = P, As, Sb, not only conduct but do so better than the analogous amorphous phases! It is also shown that the conductivities of all three 6:1 complexes are similar, consistent with the dimension of the bottlenecks to conduction derived from their crystal structures. An increase in ionic conductivity with reduction of molecular weight of the Crystalline Polymer electrolyte (from 2000 to 1000) is reported and shown to relate to the increase in...
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Ionic conductivity in Crystalline Polymer electrolytes
Nature, 2001Co-Authors: Z. Gadjourova, D. P. Tunstall, Yuri G Andreev, Peter G BruceAbstract:Polymer electrolytes are the subject of intensive study, in part because of their potential use as the electrolyte in all-solid-state rechargeable lithium batteries. These materials are formed by dissolving a salt (for example LiI) in a solid host Polymer such as poly(ethylene oxide) (refs 2, 3, 4, 5, 6), and may be prepared as both Crystalline and amorphous phases. Conductivity in Polymer electrolytes has long been viewed as confined to the amorphous phase above the glass transition temperature, Tg, where Polymer chain motion creates a dynamic, disordered environment that plays a critical role in facilitating ion transport. Here we show that, in contrast to this prevailing view, ionic conductivity in the static, ordered environment of the Crystalline phase can be greater than that in the equivalent amorphous material above Tg. Moreover, we demonstrate that ion transport in Crystalline Polymer electrolytes can be dominated by the cations, whereas both ions are generally mobile in the amorphous phase. Restriction of mobility to the lithium cation is advantageous for battery applications. The realization that order can promote ion transport in Polymers is interesting in the context of electronically conducting Polymers, where crystallinity favours electron transport.
Zeyu Liu - One of the best experts on this subject based on the ideXlab platform.
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Crystalline Polymer nanofibers with ultra high strength and thermal conductivity
Nature Communications, 2018Co-Authors: Ramesh Shrestha, Bikramjit Chatterjee, Teng Zheng, Zeyu Liu, Tengfei Luo, Sukwon Choi, Kedar Hippalgaonkar, Maarten P De Boer, Sheng ShenAbstract:Polymers are widely used in daily life, but exhibit low strength and low thermal conductivity as compared to most structural materials. In this work, we develop Crystalline Polymer nanofibers that exhibit a superb combination of ultra-high strength (11 GPa) and thermal conductivity, exceeding any existing soft materials. Specifically, we demonstrate unique low-dimensionality phonon physics for thermal transport in the nanofibers by measuring their thermal conductivity in a broad temperature range from 20 to 320 K, where the thermal conductivity increases with increasing temperature following an unusual ~T1 trend below 100 K and eventually peaks around 130-150 K reaching a metal-like value of 90 W m-1 K-1, and then decays as 1/T. The Polymer nanofibers are purely electrically insulating and bio-compatible. Combined with their remarkable lightweight-thermal-mechanical concurrent functionality, unique applications in electronics and biology emerge.
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Crystalline Polymer nanofibers with ultra-high strength and thermal conductivity
Nature Communications, 2018Co-Authors: Ramesh Shrestha, Bikramjit Chatterjee, Teng Zheng, Zeyu Liu, Tengfei Luo, Sukwon Choi, Kedar Hippalgaonkar, Maarten P De Boer, Sheng ShenAbstract:Polymers are widely used in daily life, but exhibit low strength and low thermal conductivity as compared to most structural materials. In this work, we develop Crystalline Polymer nanofibers that exhibit a superb combination of ultra-high strength (11 GPa) and thermal conductivity, exceeding any existing soft materials. Specifically, we demonstrate unique low-dimensionality phonon physics for thermal transport in the nanofibers by measuring their thermal conductivity in a broad temperature range from 20 to 320 K, where the thermal conductivity increases with increasing temperature following an unusual ~ T ^1 trend below 100 K and eventually peaks around 130–150 K reaching a metal-like value of 90 W m^−1 K^−1, and then decays as 1/ T . The Polymer nanofibers are purely electrically insulating and bio-compatible. Combined with their remarkable lightweight-thermal-mechanical concurrent functionality, unique applications in electronics and biology emerge. Polymers compared to structural materials usually have low strength and thermal conductivity. Here the authors show a fabrication method to form bio-compatible Crystalline polyethylene nanofibers that exhibit ultra-high strength, thermal conductivity and electrical insulation.