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Copolymerization Reactions (copolymerization + reaction)
Selected AbstractsFabrication of novel conjugated polymer nanostructure: Porphyrins and fullerenes conjugately linked to the polyacetylene backbone as pendant groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2005Ning Wang Abstract A new series of conjugated polyacetylenes with conjugately linked fullerene and porphyrin groups as pendant units were prepared by a copolymerization reaction catalyzed by chloronorbornadiene rhodium(I)dimer-triethylamine ([Rh(nbd)Cl]2 -NEt3) in anhydrous CHCl3. These polymers were characterized with UV,vis spectroscopy, fluorescence spectroscopy, and voltammetry. Scanning electron microscopy indicated that the morphology of the copolymers consisted of uniform nanorods with a diameter of about 100 nm and a length of about 300 nm. Thin films of the copolymers produced steady and prompt photocurrent at an irradiation of 20.0 mW cm,2 of white light, which was higher than that of a mixture of poly[5-(4-Ethynyl-phenyl)-10,15,20-tris(4-carbomethoxyphenyl)porphyrin zinc] and C60. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2851,2861, 2005 [source] Poly(ethylene glycol) Surface Coated Magnetic ParticlesMACROMOLECULAR RAPID COMMUNICATIONS, Issue 18 2005Christophe Flesch Abstract Summary: A methacrylate-functionalized poly(ethylene glycol) macromonomer was copolymerized at the surface of methacrylate-derivatized maghemite nanoparticles. After silylation of the magnetic core with methacryloxypropyltrimethoxysilane, two grafting procedures based on either a direct copolymerization reaction in water or an inverse emulsion polymerization were compared. A direct copolymerization led to low polymer surface amounts, whereas an inverse emulsion process allowed nanocomposite particles containing up to 90 wt.-% polymer to be obtained. TEM picture of maghemite-PEG hybrid particles. [source] Preparation of a Transparent Spherical Polymer Matrix Containing TiO2/SiO2 Hybrid MaterialsCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 4 2008D.-H. Zhang Abstract A transparent spherical polymer matrix containing TiO2/SiO2 hybrid materials is prepared from the copolymerization reaction between TiO2/SiO2 hybrid materials containing vinyl groups and methyl methacrylate (MMA). Transparent TiO2/SiO2 hybrid materials are prepared from the reaction between nucleophilic agents and tetrabutyl titanate (TBT). Three reaction mechanisms leading to the formation of nanometer TiO2/SiO2 hybrid materials, including the single group coordination reaction mechanism (SGCRM), double group chelation reaction mechanism (DGCRM) and bridge coordination reaction mechanism (BCRM) are discussed in detail and confirmed by FT-IR spectroscopy. The sizes of the TiO2/SiO2 hybrid material nanoparticles are also characterized and calculated by TEM and range from 20,40,nm. The diameter of the particles in the transparent spherical polymer matrix is ca. 100,200,nm and their shape is a regular spherical structure from TEM observations. The transparent spherical polymer matrix containing TiO2/SiO2 hybrid materials could be used as holographic anti-counterfeiting materials. [source] Copolymerization of Cyclohexene Oxide with CO2 by Using Intramolecular Dinuclear Zinc CatalystsCHEMISTRY - A EUROPEAN JOURNAL, Issue 12 2005Youli Xiao Abstract The intramolecular dinuclear zinc complexes generated in situ from the reaction of multidentate semi-azacrown ether ligands with Et2Zn, followed by treatment with an alcohol additive, were found to promote the copolymerization of CO2 and cyclohexene oxide (CHO) with completely alternating polycarbonate selectivity and high efficiency. With this type of novel initiator, the copolymerization could be accomplished under mild conditions at 1 atm pressure of CO2, which represents a significant advantage over most catalytic systems developed for this reaction so far. The copolymerization reaction was demonstrated to be a living process as a result of the narrow polydispersities and the linear increase in the molecular weight with conversion of CHO. In addition, the solid-state structure of the dinuclear zinc complex was characterized by X-ray crystal structural analysis and can be considered as a model of the active catalyst. On the basis of the various efforts made to understand the mechanisms of the catalytic reaction, including MALDI-TOF mass analysis of the copolymers' end-groups, the effect of alcohol additives on the catalysis and CO2 pressure on the conversion of CHO, as well as the kinetic data gained from in situ IR spectroscopy, a plausible catalytic cycle for the present reaction system is outlined. The copolymerization is initiated by the insertion of CO2 into the ZnOEt bond to afford a carbonate,ester-bridged complex. The dinuclear zinc structure of the catalyst remains intact throughout the copolymerization. The bridged zinc centers may have a synergistic effect on the copolymerization reaction; one zinc center could activate the epoxide through its coordination and the second zinc atom may be responsible for carbonate propagation by nucleophilic attack by the carbonate ester on the back side of the cis -epoxide ring to afford the carbonate. The mechanistic implication of this is particularly important for future research into the design of efficient and practical catalysts for the copolymerization of epoxides with CO2. [source] Kinetics of radical copolymerization of [1-(fluoromethyl)vinyl]benzene with chlorotrifluoroethyleneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2007G. Kostov Abstract The synthesis of [1-(fluoromethyl)vinyl]benzene (or ,-(fluoromethyl)styrene, FMB) and its radical copolymerization with chlorotrifluorethylene (CTFE), initiated by tert -butyl peroxypivalate (TBPPi) are presented. The allyl monomer [H2C = C(CH2F)C6H5] was obtained by electrophilic fluorodesilylation of trimethyl(2-phenylprop-2-en-1-yl)silane in 93% yield. A series of seven copolymerization reactions were carried out starting from initial [CTFE]0/([FMB]0 + [CTFE]0) molar ratios ranging from 19.6 to 90.0 mol %. The molar compositions of the obtained poly(CTFE- co -FMB) copolymers were assessed by means of 19F nuclear magnetic resonance spectroscopy. Statistic copolymers were produced with molar masses ranging between 13,800 and 25,600 g/mol. From the Kelen and Tudos method, the kinetics of the copolymerization led to the determination of the reactivity ratios, ri, of both comonomers (rCTFE = 0.4 ± 0.2 and rFMB = 3.7 ± 1.8 at 74 °C) showing that FMB is more reactive than CTFE as well as other halogenated or nonhalogenated monomers involved in the radical copolymerization with CTFE. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3843,3850, 2007 [source] Synthesis of macroporous polymer rods based on an acrylamide derivative monomerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2006Ruben Dario Arrua Abstract New macroporous polymer rods were prepared by free-radical crosslinking copolymerization from N -acryloyl-tris(hydroxymethyl)aminomethane and N,N,-methylenebisacrylamide as a crosslinking agent with different porogenic mixtures and with azobisisobutyronitrile as an initiator. The porous properties of these materials were controlled through changes in the proportions of the porogenic mixture, the polymerization temperature, or the concentration of the crosslinking agent. Pore size distribution profiles that shifted toward a larger pore size were obtained in the following cases: when the percentage of the coporogen was increased, when the copolymerization reactions were carried out at a low temperature (55 °C), and when the crosslinking concentration was reduced. Alternatively, a porogenic mixture formed from dimethyl sulfoxide and a 1:1 combination of tetradecanol and poly(ethylene glycol) 6000 as coporogens yielded a polymer rod with a high porosity and pore size. These hydrophilic materials are promising as base supports for different chromatographic processes and as throughput bioreactors. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6616,6623, 2006 [source] Synthesis and polymerization of fluorinated monomers bearing a reactive lateral group.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2003Abstract The radical copolymerization in solution of vinylidene fluoride (VDF; or 1,1-difluoroethylene) with methyl 1,1-dihydro-4,7-dioxaperfluoro-5,8-dimethyl non-1-enoate (MDP) initiated by di- tert -butyl peroxide is presented. Six copolymerization reactions were investigated with initial [VDF]0/[MDP]0 molar ratios of 35/65 to 80/20. Both of these comonomers copolymerized in this range of copolymerization. Moreover, these comonomers homopolymerized separately under these conditions. The copolymer compositions of these random copolymers were calculated by means of 19F NMR spectroscopy, which allowed the quantification of the respective amounts of each monomeric unit in the copolymers. The Tidwell,Mortimer method was used for the assessment of the reactivity ratios (ri) of both comonomers, which showed a higher incorporation of MDP in the copolymers (rMDP = 2.41 ± 2.28 and rVDF = 0.38 ± 0.21 at 120 °C). The Alfrey,Price Q and e values of the trifluoroallyl monomer MDP were calculated to be 0.024 (from QVDF = 0.008) or 0.046 (from QVDF = 0.015) and 0.70 (vs eVDF = 0.40) or 0.80 (vs eVDF = 0.50), respectively, indicating that MDP was an electron-accepting monomer. The thermal properties of these fluorinated copolymers were also determined. Except for those containing a high amount of VDF, the copolymers were amorphous. Each showed one glass-transition temperature (Tg) only, and with known laws of Tg's, Tg of the MDP homopolymer was assessed. It was compared to that obtained from the direct radical homopolymerization of MDP and discussed. Indeed, these two values were close (Tg = ,3 °C). Thermogravimetric analyses were performed, and they showed that the copolymers were rather thermostable because the thermal degradation occurred at 280 °C. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3109,3121, 2003 [source] Multicenter nature of titanium-based Ziegler,Natta catalysts: Comparison of ethylene and propylene polymerization reactionsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2003Yury V. Kissin Abstract This article discusses the similarities and differences between active centers in propylene and ethylene polymerization reactions over the same Ti-based catalysts. These correlations were examined by comparing the polymerization kinetics of both monomers over two different Ti-based catalyst systems, ,-TiCl3 -AlEt3 and TiCl4/DBP/MgCl2 -AlEt3/PhSi(OEt)3, by comparing the molecular weight distributions of respective polymers, in consecutive ethylene/propylene and propylene/ethylene homopolymerization reactions, and by examining the IR spectra of "impact-resistant" polypropylene (a mixture of isotactic polypropylene and an ethylene/propylene copolymer). The results of these experiments indicated that Ti-based catalysts contain two families of active centers. The centers of the first family, which are relatively unstable kinetically, are capable of polymerizing and copolymerizing all olefins. This family includes from four to six populations of centers that differ in their stereospecificity, average molecular weights of polymer molecules they produce, and in the values of reactivity ratios in olefin copolymerization reactions. The centers of the second family (two populations of centers) efficiently polymerize only ethylene. They do not homopolymerize ,-olefins and, if used in ethylene/,-olefin copolymerization reactions, incorporate ,-olefin molecules very poorly. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1745,1758, 2003 [source] Matrix Representation of Polymer Chain Size Distributions, 3 , Case Studies for Linear Polymerization Mechanisms at Transient ConditionsMACROMOLECULAR THEORY AND SIMULATIONS, Issue 4-5 2008Heloísa L. Sanches Abstract The mass balance equations used to describe different polymerization systems are represented and analyzed with the help of a general matrix framework previously developed. Some of its properties were presented in previous works and are illustrated here in three examples. The first example regards the dynamics of a copolymerization reactor. It is shown that terminal and penultimate models may predict qualitatively different responses in batch reactions. The second example also regards the dynamics of copolymerization reactions. It is shown how manipulation of initial conditions and monomer feed rates can be used to keep copolymer composition constant throughout the batch. The third example concerns the existence of oscillating chain size distributions when there are multiple monomer insertion steps. [source] | |||||||||||||