Toughening of Propylene‐ethylene Copolymer/Calcium Carbonate Composites with High‐Density Polyethylene

Propylene‐ethylene copolymer/calcium carbonate (CaCO₃) composites (weight ratio=50/50) toughened with high density polyethylene (HDPE) were prepared using a twin‐screw extruder; the HDPE content in composites was in the range of 0–4 wt.%. The notched impact strength of propylene‐ethylene copolymer/CaCO₃ composites with 1.5 wt.% HDPE was 46% higher than that of propylene‐ethylene copolymer/CaCO₃ composites. Differential scanning calorimetry (DSC) experiments showed that good miscibility between propylene‐ethylene copolymer and HDPE enhanced the interpenetration of the macromolecules located in the interface. It was shown that debonding of the small HDPE particles within the propylene‐ethylene copolymer matrix resulted in the formation of small voids; the subsequent plastic deformation of the propylene‐ethylene copolymer matrix next to the voids thinned the ligaments and led to large energy consumption.     

Mesostructures and properties of transparent block copolymer/silica nanocomposite monoliths

In this work, three different block copolymer/silica hybrid nanocomposite monoliths that possess mesostructured domains (hexagonal, cubic, and disordered) were prepared through the micellization of the block copolymer during the sol-gel process of a silica precursor. Transparent block copolymer/silica nanocomposite monoliths were obtained from the amphiphilic triblock copolymer poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (EO₁₀₆PO₇₀EO₁₀₆, Pluronic F127), which we used to organize the polymerizing silica networks; the ratio between the block copolymer and silica was fixed at 60:40 (wt%). Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) were used to observe the mesostructural ordering. Temperature-dependent SAXS patterns of the cubic structured nanocomposites showed that the calcination process takes place at 210°C. The transmittances of the nanocomposite monoliths over the range of wavelengths from 400 to 800 nm was >85%. From rheological measurements at low frequency, it was found that the hexagonally structured monoliths had higher storage and loss moduli relative to the monoliths possessing cubic and disordered structures.     

Features of crystallization of chitosan with different molecular mass and its mixtures with pluronic F-127 according to atomic force microscopy and X-ray diffraction data

The structure of chitosan with different molecular mass and its mixtures with pluronic F-127 (triblock copolymer of ethylene and propylene oxide) crystallized from aqueous solutions was analyzed by atomic force microscopy and X-ray diffraction methods. It was established that the low-molecular-mass chitosan (M_w = 20000) had a highly ordered macrocrystalline structure, whereas the high-molecular-mass chitosan (M_w = 250000) was characterized by a poorly ordered quasi-crystalline structure. It was shown that, after evaporation of the aqueous solution of high-molecular-mass chitosan and pluronic F-127, chitosan formed a continuous film on the mica surface and pluronic formed dendritic structures on the chitosan surface. At the same time, the evaporation of the solution of the low-molecular-mass chitosan and pluronic F-127 mixture resulted in the formation of interpenetrating dendrites of chitosan and pluronic on the mica surface. In the low-molecular-mass chitosan-pluronic systems, a pluronic crystalline phase was formed at a lower pluronic content than in the case of high-molecular-mass chitosan-pluronic systems.     

Nanostructured Thermosetting Blends of Phenolic Thermosets and Poly(ethylene oxide)‐block‐poly(propylene oxide)‐block‐poly(ethylene oxide) Triblock Copolymer

The amphiphilic triblock copolymer, poly(ethylene oxide)‐block‐poly(propylene oxide)‐block‐poly(ethylene oxide) (PEO‐b‐PPO‐b‐PEO) was incorporated into novolac resin to prepare thermosetting blends. The morphology of the thermosetting blends was investigated by means of atomic force microscopy (AFM) and small‐angle x‐ray scattering (SAXS) and the nanostructures were obtained. It was identified that the reaction‐induced phase separation occurred in the blends of phenolic thermosets with the model poly(propylene oxide) (PPO), whereas poly(ethylene oxide) (PEO) was miscible with novolac resin after and before the curing reaction. In terms of miscibility and phase behavior of the subchains of the triblock copolymer with novolac resin, it was demonstrated that the formation of nanostructures in the thermosets followed a mechanism of reaction‐induced microphase separation.     

Effect of EPDM Content on Melt Flow,Microstructures and Fracture Behavior of Dynamically Vulcanized PP/EPDM Blends

Polypropylene (PP)/Ethylene‐propylene‐diene terpolymer (EPDM) blends were dynamically vulcanized with dicumyl peroxide (DCP), using a two‐step method of even dispersion of DCP in EPDM at first and then cross‐linking at elevated temperature. The results showed that though both chain scission and cross‐linking occurred, the cross‐linking reaction predominated in this process and the number of EPDM particles was increased, accompanied with a reduction in particle size and uniform dispersion. Differential scanning calorimetry (DSC) results indicated the existence of PP/EPDM graft copolymer. The essential work of fracture (EWF) results showed that both the specific essential work of fracture (w _e ) and the specific plastic work (w _p ) increased with increasing EPDM content, the fracture toughness and plastic energy consumption (βw _p ) could be improved simultaneously and the ratio of w _e and βw _p could be controlled by adjusting EPDM and DCP content.     

有序TiO2纳米管阵列结构的可控生长及其物相研究

分别在HF水溶液、含NH₄F和H₂O的乙二醇有机溶液中对Ti箔进行阳极氧化,得到TiO₂纳米管阵列结构.该结构高度有序、分布均匀、垂直取向,且通过阳极氧化工艺条件(如阳极氧化电压、电解液的选择与配比以及氧化时间等)可实现对其结构参数(如管径、管壁厚度、管密度、管长等)的有效控制.利用XRD研究了TiO₂纳米管阵列的物相结构.结果表明：退火前的TiO₂纳米管阵列为无定形结构;分别在真空和氧气氛中50 关键词： 2纳米管阵列')" href="#">TiO₂纳米管阵列 阳极氧化 可控生长     

Preparation of Aromatic Polycarbonate Nanoparticles using Supercritical Carbon Dioxide

A novel synthetic process for producing aromatic polycarbonate (PC) nanoparticles using supercritical CO₂ was developed. The objective of the present research work was to synthesize high molecular weight PC nanoparticles using transesterification between bisphenol-A (BPA) and diphenyl carbonate (DPC) in supercritical CO₂ which is an excellent plasticizing agent and a good solvent for phenol, a by-product of the reaction. Poly(propylene oxide)–poly(ethylene oxide)–poly(propylene oxide) tri-block copolymer with CO₂-phobic anchor and CO₂-philic tail group was used as a stabilizer for the preparation of stable dispersions of BPA–DPC mixture in a CO₂ continuous phase. As the reaction was proceeding, phenol formed from the reaction was dissolved and diffused into supercritical CO₂ phase. The PC nanoparticles were isolated by simple venting of the supercritical CO₂ from the reactor. Spherical morphology of PC particles was confirmed by scanning electron microscopy. Particle size and morphology of PC particles were modified upon variation of the process conditions. The resulting PC particles with a nano-size of 30–140nm have a high molecular weight (M _w) of 3.1×10⁵ (g/mol).     

Stimuli-responsive poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide) triblock copolymers and complexation with poly(acrylic acid) at low pH

The self-organization of the double hydrophilic triblock copolymer poly(ethylene oxide)-b-poly(2-vinylpyridine)-b-poly(ethylene oxide), PEO-b-P2VP-b-PEO, was investigated in dilute aqueous solution under several experimental conditions using turbidimetry, as well as static and dynamic light scattering. As a result of the temperature-sensitive properties of the end PEO blocks and the p H-responsive properties of the middle P2VP block, the formation of large star-like micellar nanostructures is observed at high p H, while at low p H, but in the presence of salt and at high temperature, flower-like micelles are formed. Moreover, the viscosimetric and dynamic light scattering studies at low p H revealed that micelle-like nanostructures are formed upon mixing the triblock copolymer with poly(acrylic acid), PAA, due to hydrogen bonding interpolymer complexation.     

Injection Molding Shrinkage and Mechanical Properties of Polypropylene Blends

Polypropylene (PP) blends based on isotactic polypropylene (iPP), propylene-ethylene block copolymer (bPP), and propylene–ethylene random copolymer (rPP) were prepared by melt blending and the effects of content of bPP and rPP on the shrinkage during solidification and storage and mechanical properties of the blends were studied. It was found that the addition of polypropylene copolymer could effectively reduce the processing shrinkage of iPP and the lowest shrinkage of the blends was achieved at a loading of 2 wt% bPP or rPP. The flexural modulus and tensile strength of the blends decreased a little while the impact strength and elongation at break were improved greatly compared with those of iPP.     

Polypropylene Nanocomposites Based on Synthetic Organic-Soluble Ag Nanocrystals with Prominent β-nucleating Effect: Quiescent Crystallization and Melting Behavior

Differential scanning calorimetry, x-ray diffraction, and polarized optical microscopy were used to investigate the quiescent crystallization and melting behavior of isotactic polypropylene (iPP) nanocomposites based on synthetic organic-soluble Ag nanocrystals (NCs). The effects of Ag loading and crystallization temperature on the crystallization behavior and crystalline structure were studied. The results showed that the synthetic Ag NCs as a novel effective β-crystal nucleating agent for iPP could promote the overall crystallinity, decrease the size of spherulites, and induce the formation of large amounts of β-crystals in the nanocomposites under quiescent crystallization. The relative content of β-crystals significantly increased with increasing Ag loading, and slightly increased with decreasing crystallization temperature. The quiescent crystallization kinetics was analyzed using the Avrami model. The results showed that the iPP nanocomposites with added Ag NCs had higher crystallization rate constant (k) and lower crystallization half-times (t_1/2) as well as the Avrami exponent (n) than pure iPP, indicating that the presence of Ag NCs acted as heterogeneous nucleating sites and promoted the crystallization rate of iPP.     

Nonisothermal Crystallization of Recycled Poly(Ethylene Terephthalate)/Poly(Ethylene Octene) Blends

Recycled poly(ethylene terephthalate) (r-PET) was blended with poly(ethylene octene) (POE) and glycidyl methacrylate grafted poly(ethylene octene) (mPOE). The nonisothermal crystallization behavior of r-PET, r-PET/POE, and r-PET/mPOE blends was investigated using differential scanning calorimetry (DSC). The crystallization peak temperatures (T _p ) of the r-PET/POE and r-PET/mPOE blends were higher than that of r-PET at various cooling rates. Furthermore, the half-time for crystallization (t _1/2 ) decreased in the r-PET/POE and r-PET/mPOE blends, implying the nucleating role of POE and mPOE. The mPOE had lower nucleation activity than POE because the in situ formed copolymer PET-g-POE in the PET/mPOE blend restricted the movement of PET chains. Non-isothermal crystallization kinetics analysis was carried out based on the modified Avrami equation, the Ozawa equation, and the Mo method. It was found that the Mo method provided a better fit for the experimental data for all samples. The effective energy barriers for nonisothermal crystallization of r-PET and its blends were determined by the Kissinger method.     

Study of the Interaction Between Apis mellifera Venom and Micro-Heterogeneous Systems

The bee venom, used in treatment of inflammatory and articular diseases, is a complex mixture of peptides and enzymes and the presence of tryptophan allows the investigation by fluorescence techniques. Steady state and time-resolved fluorescence spectroscopy were used to study the interaction between bee venom extracted from Apis mellifera and three micro heterogeneous systems: sodium dodecylsulphate (SDS) micelles, sodium dodecylsulphate-poly(ethylene oxide) (SDS-PEO) aggregates, and the polymeric micelles LUTROL^® F127, formed by poly(ethylene oxide)-poly(propylene oxide)- poly(ethylene oxide). Fluorescence parameters in buffer solution were typical of peptides containing tryptophan exposed to the aqueous medium, and they gradually changed upon the addition of surfactant and polymeric micelles, demonstrating the interaction of the peptides with the micro heterogeneous systems. Quenching experiments were carried out using the N-alkylpyridinium ions (ethyl, hexyl, and dodecyl) as quenchers. In buffer solution the quenching has low efficiency and is independent of the alkyl chain length of the quencher. In the presence of the micro heterogeneous systems the extent of static and dynamic quenching enhanced, showing that both fluorophore and quenchers reside in the microvolume of the aggregates. The more hydrophobic quencher (dodecyl pyridinium ion) provides higher values for K _SV and dynamic quenching constants, and SDS-PEO aggregates are most efficient to promote interaction between peptides and alkyl pyridinium ions. The results proved that bee venon interacts with drug delivery micelles of the copolymer LUTROL^® F127.     

Crystallization of α and γ Phases in Isotactic Polypropylene with Low Ethylene Content: Isothermal Crystallization and Secondary Crystallization

Crystallization and melting behaviors of isotactic polypropylene (iPP) with low ethylene content during an isothermal process and on heating just after it are investigated by means of in situ x-ray diffraction. At every isothermal temperature investigated here, the formations of α and γ phases are confirmed. The ratio of γ to α increases with an increase in isothermal temperature. On heating just after the isothermal process, the γ starts melting at a lower temperature than the α. This may be due to the small crystallite size of the γ crystallization during the isothermal process. On cooling after the completion of the isothermal crystallization, the secondary crystallization accelerates, and the γ phase crystallizes predominantly. The fractionation is considered to occur in the primary crystallization during the isothermal process. The low-molecular-weight portion of the materials, which remained in amorphous regions of the spherulite during the isothermal process, crystallizes into the γ phase in the secondary crystallization. Furthermore, the fractionation behavior seems to be enhanced at higher temperatures.     

Role of Cl ions in photooxidation of propylene on TiO2 surface

The effect of Cl⁻ ions on photooxidation of propylene on TiO₂ semiconductor was investigated. Cl⁻/TiO₂ catalysts were prepared by annealing Degussa P25 TiO₂ in the gas flow of N₂ and Cl₂ under 100-400 °C. The photocatalytic oxidation of propylene was carried out in a continuous flow system, with the chromatograph to analyze the products on line. The experimental results showed that the activity of Cl⁻/TiO₂ catalysts increased as heat-treated temperature decreased. The activity of the sample heat-treated at 100 °C was about two times higher than that of pure TiO₂. Moreover, as to TiO₂, the main product of the propylene photocatalytic oxidation was CO₂, but with Cl⁻/TiO₂ catalysts, not only CO₂ but also trace CO was determined. The adsorbed species on TiO₂ surface before and after reaction were analyzed by X-ray photoelectron spectroscopy (XPS) and thermogravimetric/differential thermal analyses (TG-DTA) coupled to a mass spectrometer (MS). XPS analysis showed that there was Cl⁻ absorbed on the Cl⁻/TiO₂ surface, and the absorption amount of Cl⁻ decreased after the photooxidation reaction of propylene. TG-DTA-MS analysis confirmed chlorine absorbed on the surface of TiO₂ in the form of Cl⁻ ion. These results illuminated that absorbed Cl⁻ on the surface of TiO₂ formed a weak physical absorption on TiO₂ at low temperature, and subsequently participated in the photooxidation of propylene, finally removed from TiO₂ surface.     

The role of copper species on Cu/γ-Al2O3 catalysts for NH3-SCO reaction

UV-vis spectra, XRD, H₂-TPR, TEM and ESR were used to characterize a series of Cu/γ-Al₂O₃ catalysts, which were prepared by incipient wetness impregnation using copper nitrate, copper acetate or copper sulfate as precursors, to study the role of Cu species on Cu/γ-Al₂O₃ catalysts for NH₃-SCO reaction. It was found that the mixture of CuO phase and CuAl₂O₄ phase formed on various Cu/γ-Al₂O₃ catalysts, and the Cu species and dispersion had significant influence on the Cu/γ-Al₂O₃ activity. Highly dispersed CuO phase on the support would be related with its high activity for the NH₃-SCO reaction.     

Annealing Induced Degradation of Thermal SiO2 On (100)Si: Point Defect Generation

The structural degradation of thermal SiO₂ on (100)Si under isochronal post oxidation vacuum annealing (POVA) has been probed by electron spin resonance (ESR). The degradation process, studied in the range T_an = 950–1250 °C, is established as intense point defect generation including E′_γ, E′_δ, EX and the elusive predominant degradation center S. Thermally activated generation is revealed over broad T_an ranges for the two most populous defects, S and E′_γ, with a common activation energy ～1.6eV. Depth profiling after heating at 1200°C shows that the S centers predominantly reside near the oxide borders, generally in anticorrelation with the E′_γ distribution. The S center susceptibility has been inferred from conventional ESR signal intensity monitoring as well as from revealed anisotropic demagnetisation effects. It is found Curie-Weiss type with critical temperature of ～ 1.3 K. Newly observed weak hyperfine structure may comply with the S center being an E′-like defect.     

Photocatalytic behavior of heavy La-doped TiO2 films deposited by pulsed laser deposition using non-sintered target

We have investigated the control of photocatalytic behavior under deposited conditions of non-sintered target of different molar ratios with TiO₂ and La₂O₃ from 1:0 to 1:2 for heavily La doping, and post-annealing temperature from 600 °C to 1000 °C for crystallizing by pulsed laser deposition. We have successfully crystallized heavily La-doped TiO₂ films with post-annealing temperature over 800 °C and with molar ratio of TiO₂:La₂O₃ over 1:1 on a quartz substrate. Heavily La-doped TiO₂ films are observed the decomposition of methylene blue and a water-splitting reaction in photocatalytic behavior under Xe light irradiation. When stoichiometric La-doped TiO₂ (TiO₂:La₂O₃ = 1: 1) is synthesized with heat-treatment at 900 °C, the best results are obtained under photocatalytic behavior and pure La₂Ti₂O₇ crystalline were obtained.     

Preparation of Al(OH)3/Acrylic Copolymer Latex by Emulsion Polymerization

The Al(OH)₃/acrylic copolymer latexes were synthesized through the emulsion polymerization of acrylic monomers, butyl acrylate and 2-ethylhexyl acrylate in the presence of surface-functionalized Al(OH)₃ filler particles. The polymerization was stabilized by polyoxyethylene (50) nonyl phenyl ether (NP-1050, nonionic surfactant) and ammonium (POE) alkyl aryl ether sulfate (EU-S133D, anionic surfactant) to produce stable composite latexes. The improved compatibility of Al(OH)₃ surface with acrylic monomers was achieved by the modification with 3-(trimethoxysilyl) propyl methacrylate (γ-MPS). Transmission electron microscopy showed that nano-sized Al(OH)₃ particles were slightly agglomerated in the copolymer latex. When pristine Al(OH)₃ was used as a filler or γ-MPS-modified Al(OH)₃ particles were added above 30 wt% with respect to monomers, unstable latexes were obtained, which were partially precipitated out on standing for prolonged time. The flame retardation effect was not apparent with the incorporation of Al(OH)₃ in the latexes by 30 wt% as shown by LOI test.     

Influence of nanocrystalline phases on the electrical properties of lithium titanate phosphate glass ceramics mixed with Ga2O3 nanocrystals

Several glass ceramic compositions dispersed with Ga₂O₃ nanocrystals, in the series samples (100???x)[0.4Li₂O–0.1TiO₂–0.5P₂O₅]?+?xGa₂O₃ with x?=?0, 2, 4, 6, 8, and 10?mol% of Ga₂O₃ were synthesized via high-energy ball milling technique and labeled as lithium gallium titanate phosphate glass (LTPG _x ) (x is the mol% of Ga₂O₃ nanocrystals). The compositions have been selected on the basis of thermal stability data obtained from differential thermal analysis. X-ray diffraction studies indicate nanocrystalline phase formation in the controlled crystallized glasses. The variation of electrical conductivity was explained in the light of growth of nanocrystalline phases. The best bulk conductivity (σ?=?7.03?×?10^?4?S?cm^?1, at 303?K) was achieved by the sample containing 8?mol% of Ga₂O₃ nanocrystals content, labeled as LTPG₈ sample. The activation energy for conduction (E_{a σ} ) is obtained from the temperature dependent of conductivity data, which is fitted to Arrhenius equation. The single super curve in the scaling spectra suggested the temperature-independent relaxation phenomenon.     

Step-addition Method for Enhancing the Yield of Gold Nanoparticles in Block Copolymer Solution

Triblock copolymer poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) has been used to synthesize gold nanoparticles from hydrogen tetrachloroaureate (III) hydrate (HAuCl₄·3H₂O) salt in aqueous solution at room temperature. Measurements were performed using the triblock copolymer Pluronic P85 (EO₂₆PO₃₉EO₂₆) at a fixed concentration (1 wt%) mixed with varying HAuCl₄·3H₂O concentration in the range of 0.001 to 0.1 wt%. The surface plasmon resonance (SPR) band in UV-visible absorption spectra confirmed the formation of the gold nanoparticles. The maximum yield of the nanoparticles was found at 0.005 wt% of the salt solution. Small-angle neutron scattering (SANS) does not show any significant change in the scattering profile in these suspensions of the nanoparticles. A similar behavior was also observed in dynamic light scattering (DLS) experiments where autocorrelation function was found to be independent of the salt concentration. This can be understood since a high-block copolymer-to-gold ion ratio (r ～ 22) is required in the reduction reaction to produce gold particles. As a result, a very small fraction of the block copolymers were associated with the gold nanoparticles, and hence lead to a very low yield. Both SANS and DLS basically see the micelles of most of these block copolymers, which are not associated with nanoparticles. Based on this explanation, a step-addition method was used to enhance the yield of gold nanoparticles by manifold, where the gold salt is added in small steps to maintain higher value of r (>22), and therefore continuous formation of nanoparticles.