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Morphology enhancement of TiO2/PVP composite nanofibers based on solution viscosity and processing parameters of electrospinning method
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Soraya Mirmohammad Sadeghi Mohammadreza Vaezi Asghar Kazemzadeh Roghayeh Jamjah 《应用聚合物科学杂志》2018,135(23)
In this work, different sol solutions with various titanium tetraisopropoxide (TIP)/glacial acetic acid ratios in 2‐propanol with 5 wt % poly(vinyl pyrrolidone) (PVP) (Mw = 360,000 g/mol) were prepared and electrospun. Composition of the prepared sols and as‐spun TiO2/PVP nanofibers were determined by Fourier transform infrared and Raman spectroscopy methods. Morphology of the electrospun TiO2/PVP nanofibers was studied by scanning electron microscopy and transmission electron microscopy (TEM) techniques. Rheometry measurements of the sol solutions showed decrease of viscosity upon the addition of TIP to the polymer solutions with constant polymer and acid concentrations. The sol solution having the lowest viscosity (at shear rate 10 s?1) but the highest TIP/glacial acetic acid ratio showed beaded nanofibers morphology when electrospun under 10 and 12 kV applied voltage while injection rate, needle tip to collector distance, and needle gauge were kept constant. However, smooth electrospun TiO2/PVP composite nanofibers with the average nanofibers diameters (148 ± 79 nm) were achieved under the same condition when applied voltage increased to 15 kV. TEM micrographs of the electrospun TiO2/PVP nanofiber showed that the TiO2 particles with continuous structure are formed at the middle of the nanofiber and distributed along its axis. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46337. 相似文献
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Reza Teimuri Mofrad Roghieh Alizadeh Soghra Ramazani Ali Reza Vaez 《Polymer-Plastics Technology and Engineering》2018,57(9):893-902
A combination of ring-opening polymerization and atom-transfer radical polymerization was used to synthesize a four-arm star-shaped poly(ε-caprolactone)-b-poly(2-hydroxyethyl methacrylate). The structure of obtained copolymer was determined by Fourier transform infrared, 1H and 13C NMR spectroscopies. The uniform electroactive nanofibers consisting blend of four-arm star-shaped poly(ε-caprolactone)-b-poly(2-hydroxyethyl methacrylate) copolymer and polyaniline were produced using electrospinning technique. The electroactivity of prepared nanofibers was investigated using cyclic voltammetry measurement. The morphologies of electrospun nanofibers produced from four-arm star-shaped poly(ε-caprolactone)-b-poly(2-hydroxyethyl methacrylate) and their blends with polyaniline were investigated by the scanning electron microscopy. The presence of polyaniline resulted in significant decrease of sticking fibers. 相似文献
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Heterogeneous Ziegler–Natta systems—MgCl2 (ethoxide type)/TiCl4/di‐n‐butyl phthalate (DNBP)/triethylaluminum (TEA)/dimethoxymethylcyclohexylsilane (DMMCHS) and SiO2/MgCl2 (ethoxide type)/TiCl4/DNBP/TEA/DMMCHS—were studied for the polymerization of propylene. The slurry polymerization of propylene was carried out with the catalyst systems in n‐heptane. Both systems performed with optimum activity at a particular [Al]/[DMMCHS]/[Ti] molar ratio. The ratio to reach the highest activity was much lower for the bisupported catalyst system. The productivity of the bisupported catalyst was higher than that of the monosupported one. Polypropylene of a high isotacticity index (II; >96%) was obtained with both systems and did not significantly change with an increasing [Al]/[DMMCHS]/[Ti] molar ratio. The addition of hydrogen as a chain‐transfer agent reduced II of the polymers obtained with both systems. The effect of the polymerization temperature (40–75°C) on the viscosity‐average molecular weight (Mv) and II showed a decrease in both cases. The bisupported catalyst system produced a polymer with higher Mv. The effect of temperature on II was similar for both the monosupported and bisupported systems. A monomer pressure of 2.02 × 105 to 0.8 × 106 Pa increased Mv of the obtained polymer. II of the polymer slightly decreased with increasing monomer pressure. The titanium content of the catalyst was 1.70 and 3.55% for the monosupported and bisupported systems, respectively. The surface area of the bisupported catalyst was higher than that of the monosupported catalyst. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2220–2226, 2006 相似文献
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Hossein Mahdavi Alireza Badiei Gholam Hossein Zohuri Abbas Rezaee Roghieh Jamjah Saied Ahmadjo 《应用聚合物科学杂志》2007,103(3):1517-1522
An iron‐based catalyst of 2,6‐bis‐[1‐(2‐methylphenylimino)ethyl]pyridine iron dichloride was prepared. The ligand was prepared using 2,6‐diacetylpyridine as the starting chemical under controlled conditions. The preparation procedure was followed using 13C‐NMR, 1H‐NMR, FT‐IR, MS (mass spectroscopy), and elemental analysis methods. The homogeneous polymerization of ethylene was carried out using the prepared catalyst in toluene media. Methyl aluminoxane (MAO) was used as a cocatalyst. The effect of the [Al] : [Fe] molar ratio, polymerization temperature, and monomer pressure of 202,000 to 454,500 Pa on the polymerization behavior were studied. The highest activity of the catalyst was obtained at 30°C, the activity decreased with increasing temperature, while increasing pressure linearly increased its activity. The molecular weight distribution of the polyethylene obtained was 1.25 to 1.72. A weight average molecular weight of 7.1 × 104 and 1.5 × 103 were obtained. The crystallinity of the polymer was about 19% and its melting point was about 65°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1517–1522, 2007 相似文献
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Copolymerization of ethylene–propylene using high‐activity bi‐supported Ziegler–Natta TiCl4 catalyst
Heterogeneous Ziegler–Natta TiCl4 catalyst using MgCl2 and SiO2 as supports was prepared under controlled conditions. Mg(OEt)2 was used as a starting material and was expected to convert to active MgCl2 during catalyst preparation. Due to the high surface area and good morphological control, SiO2 was chosen as well. Slurry copolymerization of ethylene and propylene (EPM) was carried out in dry n‐heptane by using the catalyst system SiO2/MgCl2/TiCl4/EB/TiBA or TEA/MPT/H2 at temperatures of 40–70°C, different molar ratios of alkyl aluminum : MPT : Ti, hydrogen concentrations, and relative and total monomers pressure. Titanium content of the catalyst was 2.96% and surface area of the catalyst was 78 m2/g. Triisobutyl aluminum (TiBA) and triethyl aluminum (TEA) were used as cocatalysts, while ethyl benzoate (EB) and methyl p‐toluate (MPT) were used as internal and external donors, respectively. H2 was used as a chain‐transfer agent. Good‐quality ethylene propylene rubber (EPR) of rubber was obtained at the ratio of [TiBA] : [MPT] : [Ti] = 320 : 16 : 1 and polymerization temperature was 60°C. When TiBA was used as a cocatalyst, a higher and more rubberlike copolymer was obtained. For both of the cocatalysts, an optimum ratio of Al/Ti was obtained relative to the catalyst productivity. Ethylene content of the copolymer obtained increased with increasing TiBA concentration, while inverse results were obtained by using TEA. Addition of H2 increased the reactivity of the catalyst. The highest product was obtained when 150 mL H2/L solvent was used. Increasing temperature from 40 to 70°C decreased the productivity of the catalyst, while irregular behavior was observed on ethylene content. Relative pressure of PP/PE = 1.4 : 1 and total pressure of 1 atm was the best condition for the copolymerization. Polymers with ethylene contents of 25–84% were obtained. Increasing ethylene content of EPR decreased Tg of the polymer obtained to a limiting value. Viscosity‐average molecular weight (Mv) decreased with increasing temperature and TiBA and H2 concentration. However, increasing the polymerization time increased the Mv. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2597–2605, 2004 相似文献
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Ghasem Karim-Nezhad Roghieh Jafarloo Parisa Seyed Dorraji 《Electrochimica acta》2009,54(24):5721-5726
Stable copper (hydr)oxide modified copper electrode was prepared by cyclic voltammetry in 0.1 M NaOH solution in the potential range of −300 to 800 mV. In the first cycle the oxidation peaks of copper were observed but in the second and next cycles, they were omitted and a clean background was obtained. This indicates that an irreversible electrochemical transformation has been achieved during the first cycle and a stable layer of hydr(oxide) formed on the surface of the copper electrode. This layer protects the electrode from corrosion. This electrode can be used for electrochemical studies in the potential range of −300 to 800 mV without any interfering effects by the oxidation peaks of copper. The modified electrode was used for electrocatalytic oxidation of hydrazine. Results showed that on the bare copper electrode the oxidation peak of 10 mM hydrazine appear at 380 mV while on the copper (hydr)oxide modified copper electrode, it appear at 260 mV. About 120 mV negative shift of the peak potential indicated the catalytic activity of (hydr)oxide layer for hydrazine. The kinetic parameters were investigated by using cyclic voltammetry and chronoamperometry. 相似文献
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Generation of GPI-linked CCL5 based chemokine receptor antagonists for the suppression of acute vascular damage during allograft transplantation 总被引:1,自引:0,他引:1
Notohamiprodjo M Djafarzadeh R Mojaat A von Lüttichau I Gröne HJ Nelson PJ 《Protein engineering, design & selection : PEDS》2006,19(1):27-35
Limiting the acute vascular damage associated with leukocyte infiltration is a central issue in solid organ transplantation. The family of chemotactic cytokines (chemokines) helps to regulate leukocyte recruitment. Systemic treatment with the chemokine ligand-5 (CCL5) based antagonist Met-RANTES has previously shown to suppress acute damage to transplanted kidneys by blocking effector cell recruitment. To address problems associated with systemic long-term administration of chemokine receptor antagonists, a chemokine based reagent was designed to be integrated into endothelial surfaces of the organ just before transplantation. Proteins anchored by glycosylphosphatidylinositol (GPI), when purified and added to cells, are efficiently incorporated into their cell surface membranes. A series of modifications were introduced into the CCL5 protein to generate a functional antagonist. These included the addition of an N-terminal methionine group, a mutation to render the protein a dimer and a GPI signal sequence for surface expression. The resultant protein was stably expressed in CHO cells, GPI anchorage was confirmed and the protein purified by FPLC. Exogenously administered Met-CCL5(dimer)-GPI was efficiently inserted into the membrane of microvascular endothelial cells. The reagent is being tested in murine models of renal transplantation. The effect on subsequent immune induced damage will be assessed. 相似文献
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Roghieh Alizadeh Mohammad Karimi Reza Teimuri Mofrad Karim Asadpour-Zeynali 《Polymer-Plastics Technology and Engineering》2015,54(1):21-32
Copolymers of poly (2-hydroxyethyl methacrylate)-graft-polyaniline (PHEMA-g-PANI) were synthesized by atom-transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate using polyaniline macro-initiators. The macro-initiators were synthesized by the reaction of amine nitrogens of polyaniline with chloroacetyl choloride. The obtained polymers were characterized by FT-IR and 1H NMR spectroscopies. Uniform nanofibers consisting of blends of PHEMA-g-PANI copolymers and polycaprolactone (PCL) were prepared using an electrospinning technique. SEM was used to investigate the morphology of nanofibers produced from PHEMA-g-PANI copolymers and PCL blends. The cyclic voltammetry measurement of blends confirmed the preparation of electroactive nanofibers. 相似文献