Synthesis of Hollow Three-Dimensional Channels LiNi_(0.5)Mn_(1.5)O_4 Microsphere by PEO Soft Template Assisted with Solvothermal Method

A appropriate size with three-dimension(3 D) channels for lithium diffusion plays an important role in constructing highperforming LiNi_(0.5)Mn_(1.5)O_4(LNMO) cathode materials, as it can not only reduce the transport path of lithium ions and electrons, but also reduce the side effects and withstand the structural strain in the process of repetitive Li~+ intercalation/deintercalation. In this work, an e fficient method for designing the hollow LNMO microsphere with 3 D channels structure by using polyethylene oxide(PEO) as soft template agent assisted solvothermal method is proposed. Experimental results indicate that PEO can make the reagents mingle evenly and nucleate slowly in the solvothermal process, thus obtaining a homogeneous distribution of carbonate precursors. In the final LNMO products, the hollow 3 D channels structure obtained by the decomposition of PEO and carbonate precursor in the calcination can provide abundant electroactive zones and electron/ion transport paths during the charge/discharge process, which benefits to improve the cycling performance and rate capability. The LNMO prepared by adding 1 g PEO possesses the most outstanding electrochemical performance, which presented an excellent discharge capacity of 143.1 mAh g~(-1) at 0.1 C and with a capacity retention of 92.2% after 100 cycles at 1 C. The superior performance attributed to the 3 D channels structure of hollow microspheres, which provide uninterrupted conductive systems and therefore achieve the stable transfer for electron/ion.     

Systematic optimization of corrosion,bioactivity, and biocompatibility behaviors of calcium-phosphate plasma electrolytic oxidation (PEO) coatings on titanium substrates

To optimize the corrosion, bioactivity, and biocompatibility behaviors of plasma electrolytic oxidation (PEO) coatings on titanium substrates, the effects of five process variables including frequency, current density, duty cycle, treatment time, and electrolyte Ca/P ratio were evaluated. In our systematic study, a Taguchi design of experimental based on an L16 orthogonal array was used. For this, the coatings characteristics such as the surface roughness, wettability, rutile to anatase and Ca/P ratios, and corrosion polarization resistance were investigated. After determining the optimum process variables for each response, the apatite forming ability in SBF (bioactivity behavior) and MG63 cell attachment and flattening (biocompatibility behavior) for two groups of coatings were examined. The first group was optimized based on the maximum corrosion polarization resistance and the variables were set as the frequency of 2000 Hz, the current density of 5 A/dm², the duty cycle of 30%, the treatment time of 5 min, and the Ca/P ratio of 0.65 at. % in the electrolyte. For the second group, the maximum surface roughness, greatest Ca/P ratio, and highest wettability as well as the minimum rutile to anatase ratio in coatings, could be obtained when the variables were set as the frequency of 10 Hz, the current density of 12.5 A/dm², the duty cycle of 50%, the treatment time of 12.5 min, and the Ca/P ratio of 1.70 at. % in the electrolyte. The results showed that while both groups of coatings indicated a significant apatite forming ability and can serve as bioactive coatings, a proper attachment and flattening of cells and consequently, the favorable biocompatibility properties were seen only in the first group.     

Morphological and kinetics study of PEO/PVC blends

The kinetics of spherulite radial growth and the morphology of the compatible system PEO/PVC have been studied by optical microscopy. The usual spherulite radial growth behaviour has been found for compatible blends with PEO content higher than 70%. For lower composition, distortion of the usual spherulite morphology has been observed; the anomalies have been attributed to partial miscibility of the components.     

PEO-b-PBA对天然橡胶/高吸水树脂共混体系增容作用的研究

通过扫描电子显微镜观察了天然橡胶和高吸水树脂共混体系的微观相态结构 ,研究了两亲性嵌段共聚物PEO b PBA结构本身的吸水能力对天然橡胶和高吸水性树脂共混体系吸水性能及力学性能的影响。结果表明 ,PEO b PBA结构本身的吸水强弱对共混体系的吸水能力贡献很小 ,但却可以显著提高共混体系的吸水膨胀能力和力学性能 ,对特殊的增容作用进行了探讨     

Synthesis and applications of heterobifunctional poly(ethylene oxide) oligomers

Poly(ethylene oxide) (PEO) oligomers are employed extensively in pharmaceutical and biomedical arenas mainly due to their excellent physical and biological properties, including solubility in water and organic solvents, lack of toxicity, and absence of immunogenicity. PEO can be chemically modified and reacted with, or adsorbed onto, other molecules and surfaces. Sophisticated applications for PEO have increased the demand for PEO oligomers with tailored functionalities, and heterobifunctional PEOs are often needed. This review discusses the synthesis and applications of heterobifunctional PEO oligomers possessing amine, carboxylate, thiol, and maleimide functional groups.     

PEO/Na-MMT粉体与聚氯乙烯复合材料的制备及性能研究

通过溶胶凝胶法,制备了聚氧乙烯(PEO)和钠基蒙脱土的复合粉体PMMT,经XRD和透射电镜分析,蒙脱土在聚氯乙烯中基体进行了纳米级的分散;通过对材料力学性能、毛细管流变和TGA测试表明,PMMT对聚氯乙烯具有增韧和增强的效果,同时使PVC的流变性和热稳定性也有一定的提高。     

Effects of poly(acrylic acid) and poly(ethylene oxide) adsorption on the stability of alumina suspension

The effect of adsorbed polymer on the stability of alumina suspension was investigated. Poly(ethylene oxide) (PEO), poly(acrylic acid) (PAA) and similar kinds of polymer salts were used as a dispersant. The amount of polymer adsorbed on alumina surface and the suspension stability was measured. The pH, molecular weight, and concentration were considered as experimental parameters. PEO shows low affinity on the alumina surface while PAA has high affinity. In the case of PAA adsorption, the surface charge change by polymer adsorption influences suspension stability strongly, but not in the case of PEO adsorption. In simultaneous adsorption of PEO and PAA, the PAA concentration was fixed and PEO concentration was varied. The stability of suspension increased with increasing PEO concentration, and this is partly due to the steric stabilization by adsorption of PAA-PEO complex or adsorption of PEO through pre-adsorbed PAA and the depletion effect of non-adsorbed polymer. Suspension adsorbing sodium salts of PAA and poly(methacrylic acid) (PMA) each showed similar stability. But, when the PEO and these kinds of salts were added together to the suspension, the one with PAA sodium salt could keep a higher stability even with lower molecular weights of PEO compared with suspension with PMA sodium salt.     

AFM study of crystallization and melting of a poly(ethylene oxide) diblock copolymer containing a tablet-like block of poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} in ultrathin films

Crystallization and melting of a poly(ethylene oxide) (PEO) diblock copolymer containing a tablet-like block of poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene} (PMPCS) in ultrathin films have been studied using atomic force microscopy (AFM) coupled with a hot stage. The PEO and PMPCS block possess the number-average molecular weights (M_n) of 5300 and 2100 g/mol, respectively. The ultrathin films on the mica and glow-discharged carbon surfaces were obtained by static dilute solution casting at room temperature. Isothermal melt crystallization from ultrathin films always leads to flat-on lamellae. Selective area electron diffraction (SAED) experiments have demonstrated that the PEO blocks crystallize with a monoclinic structure identical to that of homo-PEO and the chain direction is perpendicular to the substrate. At T_c<44 °C, the monolayer crystals are dendrites. At T_c>48 °C, square-shaped crystals are formed with the (100) and (020) planes as the crystal edges. At 44 °C≤T_c≤48 °C, an intermediate monolayer morphology is observed. The monolayer thickness increases monotonically with increasing T_c. At the same T_c, the monolayer lamellae with the top and bottom amorphous layers contacting with the atmosphere and the substrate possess a significantly larger overall thickness than the long period of the crystals in bulk. For the spiral terraces induced by screw dislocation, the thickness of each terrace is close to that of the monolayer formed at the same T_c, and their melting is mainly determined by the terrace thickness.     

Poly(ethylene oxide)/Laponite nanocomposites via melt-compounding: effect of clay modification and matrix molar mass

The present study focuses on the preparation of poly(ethylene oxide) (PEO) nanocomposites based on the synthetic Laponite clay. The clay was added both in its pure form as well as organically modified with low molar mass poly(ethylene glycol) (PEG) components in order to enhance the compatibility between Laponite and PEO. Several PEG's with different end groups were used. Almost all of them were found to intercalate in the clay intergallery spacing. An order of intercalation efficiency could be established. The modified clays displayed a good thermal stability at the nanocomposite processing temperature.The nanocomposites based on the pure Laponite clay as well as the modified clays display an intercalated structure with a modest intergallery spacing. The ion-dipole modification with the PEG's was ineffective in improving the compatibility between PEO and the Laponite silicate layers. Their respective mechanical properties were found to be increased a little, which can be attributed to the low effective aspect ratio of the silicate platelets present in the nanocomposites. This is caused by the low initial aspect ratio of Laponite (w/t=25) and the limited basal spacing increase. The addition of clay does not result in nucleation of the PEO crystallisation. In contrast, the crystallisation was inhibited, resulting in decreased heat of fusions, especially for the pure Laponite nanocomposites. The nanocomposites based on the modified Laponites display a good thermal stability.     

Preparation and ionic conductivity of solid polymer electrolyte based on polyacrylonitrile‐polyethylene oxide

The transparent and flexible solid polymer electrolytes (SPEs) were fabricated from polyacrylonitrile‐polyethylene oxide (PAN‐PEO) copolymer which was synthesized by methacrylate‐headed PEO macromonomer and acrylonitrile. The formation of copolymer is confirmed by Fourier‐transform infrared spectroscopy (FTIR) measurements. The ionic conductivity was measured by alternating current (AC) impedance spectroscopy. Ionic conductivity of PAN‐PEO‐LiClO₄ complexes was investigated with various salt concentration, temperatures and molecular weight of PEO (Mn). And the maximum ionic conductivity at room temperature was measured to be 3.54 × 10^?4 S/cm with an [Li⁺]/[EO] mole ratio of about 0.1. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 461–464, 2006