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Polymerization Reaction (polymerization + reaction)
Kinds of Polymerization Reaction Selected AbstractsProteolytically Degradable Photo-Polymerized Hydrogels Made From PEG,Fibrinogen Adducts,ADVANCED ENGINEERING MATERIALS, Issue 6 2010Daniel Dikovsky Abstract We develop a biomaterial based on protein,polymer conjugates where poly(ethylene glycol) (PEG) polymer chains are covalently linked to multiple thiols on denatured fibrinogen. We hypothesize that conjugation of large diacrylate-functionalized linear PEG chains to fibrinogen could govern the molecular architecture of the polymer network via a unique protein,polymer interaction. The hypothesis is explored using carefully designed shear rheometry and swelling experiments of the hydrogels and their precursor PEG/fibrinogen conjugate solutions. The physical properties of non-cross-linked and UV cross-linked PEGylated fibrinogen having PEG molecular weights ranging from 10 to 20,kDa are specifically investigated. Attaching multiple hydrophilic, functionalized PEG chains to the denatured fibrinogen solubilizes the denatured protein and enables a rapid free-radical polymerization cross-linking reaction in the hydrogel precursor solution. As expected, the conjugated protein-polymer macromolecular complexes act to mediate the interactions between radicals and unsaturated bonds during the free-radical polymerization reaction, when compared to control PEG hydrogels. Accordingly, the cross-linking kinetics and stiffness of the cross-linked hydrogel are highly influenced by the protein,polymer conjugate architecture and molecular entanglements arising from hydrophobic/hydrophilic interactions and steric hindrances. The proteolytic degradation products of the protein,polymer conjugates proves to be were different from those of the non-conjugated denatured protein degradation products, indicating that steric hindrances may alter the proteolytic susceptibility of the PEG,protein adduct. A more complete understanding of the molecular complexities associated with this type of protein-polymer conjugation can help to identify the full potential of a biomaterial that combines the advantages of synthetic polymers and bioactive proteins. [source] Synthesis and characterization of polyacrylamides containing meso -2,3-dimercaptosuccinic acid end groupsADVANCES IN POLYMER TECHNOLOGY, Issue 1 2010Cemal Özero Abstract By using meso -2,3-dimercaptosuccinic acid-cerium(IV) sulfate and meso -2,3-dimercaptosuccinic acid-potassium permanganate redox systems, the polymerization reaction of acrylamide (AAm) monomer was examined in aqueous acidic medium at low temperatures. Water-soluble polyacrylamides bearing meso -2,3-dimercaptosuccinic acid end groups were synthesized using meso -2,3-dimercaptosuccinic acid as a reducing agent. The effects of parameters such as the molar ratio of acrylamide to initiator, temperature, polymerization time, and sulfuric acid concentration on the yields and molecular weights of polymers were investigated. The augmentation in initiator concentration resulted in a decrease in molecular weight but an increase in the yield of polymers. The increase in reaction temperature from 20 to 60°C led to a decrease in the yield from 56.80% to 20.58%. Ce(IV) and Mn(VII) ions are reduced to Ce(III) and Mn(II) ions in the polymerization reaction and the synthesized acrylamide polymers containing meso -2,3-dimercaptosuccinic acid end groups can absorb these ions at the end of the polymerization reaction. Ultraviolet-visible and atomic absorption measurements of polymer solutions were performed to indicate complexation between polyacrylamide and Ce(III) ions or Mn(II) ions. © 2010 Wiley Periodicals, Inc. Adv Polym Techn 29:45,53, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20180 [source] Syndiotactic polystyrene: Process and applicationsADVANCES IN POLYMER TECHNOLOGY, Issue 3 2006Jürgen Schellenberg Abstract In this review, a summary is provided of the manufacturing process for syndiotactic polystyrene together with an overview of applications of syndiotactic polystyrenes, including selected examples of typical applications. The manufacturing process of syndiotactic polystyrene, consists of several basic sections: catalyst premix preparation, monomer treatment, polymerization reaction using a powder bed reactor together with an evaporative cooling system, devolatilization and extrusion, and finally finishing, including cooling and crystallization of the strands. This process is suitable for providing a wide range of syndiotactic polystyrenes comprising homopolymers, with a broad range of melt flow rates as well as copolymers of various comonomer contents, leading to products with various melting temperatures. Essential relationships and correlations of the separate process stages are demonstrated, in addition to useful analytical methods to control the process. These polymers' unique combination of heat resistance, chemical resistance, and electrical properties has led to their successful application in automotive, electrical and electronics, consumer and industrial uses. © 2006 Wiley Periodicals, Inc. Adv Polym Techn 25:141,151, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/adv.20069 [source] Polymerization of linseed oil with phenolic resinsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2010Gökhan Çayl Abstract In this study, linseed oil was directly polymerized with different oil soluble resoles. p- Ethyl (PEP), p-tertiary butyl (PTB), p-tertiary octyl (PTO), and p- phenyl (PPP) phenols were separately reacted with formaldehyde to give linseed oil soluble resoles. These were then reacted with linseed oil to give transparent rubbery polymers. A model reaction was performed with methyl oleate and PTB phenol resole to clarify the reaction mechanism. Reaction products were characterized with 1H-NMR and IR techniques. Spectral examination of the model reaction showed that polymerization reaction proceeded via ene reaction of the quinone methide formed at the end group of the resole with the allylic positions of the fatty ester. Rubbery polymers were obtained with linseed oil using 10 to 40% of the different resoles. Hard, load bearing and tough materials were obtained at 40% phenolic resin loading. Mechanical properties of the materials were characterized by dynamic mechanical analyzer (DMA) and stress,strain tests. The best mechanical and thermal properties were obtained with PEP resole which showed a storage modulus of 350 MPa and a tan , peak at 65°C. Storage moduli of 275, 250, and 30 were obtained for PPP, PTB, and PTO resoles-linseed oil polymers, respectively. At the same phenolic resin loading, elongation at break and swelling ratios in CH2Cl2 increased with the longer alkyl substitution on the resole resins. The highest thermal stability was observed by PEP resole,linseed oil polymer which has a 5% weight loss temperature of 340°C as determined by TGA. The lowest thermal stability was observed for PTB resole-linseed oil polymer at 220°C. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Celite-mediated linking of polyurethane block copolymers and the impact on the shape memory effectJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010Yong-Chan Chung Abstract Celite, a porous inorganic material with enormous surface area and hydroxyl groups on the surface, was used as a cross-linker of polyurethane (PU) copolymer chains to improve its shape memory and mechanical properties. PU copolymers with different Celite contents were prepared and characterized by IR, DSC, and universal testing machine. The glass transition temperature of PU copolymers was maintained around 20°C independent of Celite content. The shape memory and mechanical properties were dependent on when Celite was added during the polymerization reaction. The reaction in which Celite was added at the middle stage of polymerization showed the best shape memory and mechanical properties. The best shape recovery of PU was found at 0.3 wt % Celite and increased to 97% even after the third cycle. Likewise, the shape retention also maintained a remarkable 86% after three cycles. The reasons underlining the high shape recovery and shape retention by adopting Celite as a cross-linker are discussed in this article. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Biodegradable poly(vinyl alcohol)- graft - poly(,-caprolactone) comb-like polyester: Microwave synthesis and its characterizationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2007Zhaoju Yu Abstract Poly(vinyl alcohol)-initiated microwave-assisted ring opening polymerization of ,-caprolactone in bulk was investigated, and a series of poly(vinyl alcohol)- graft -poly(,-caprolactone) (PVA- g -PCL) copolymers were prepared, with the degree of polymerization (DP) of PCL side chains and the degree of substitution (DS) of PVA by PCL being in the range of 3,24 and 0.35,0.89, respectively. The resultant comb-like PVA- g -PCL copolymers were confirmed by means of FTIR, 1H NMR, and viscometry measurement. The introduction of hydrophilic backbone resulted in the decrease in both melting point and crystallization property of the PVA- g -PCL copolymers comparing with linear PCL. With higher microwave power, the DP of PCL side chains and DS of PVA backbone were higher, and the polymerization reaction proceeded more rapidly. Both the DP and monomer conversion increased with irradiation time, while the DS increased first and then remained constant. With initiator in low concentration, the DP and DS were higher, while the monomer was converted more slowly. Microwaves dramatically improved the polymerization reaction in comparison of conventional heating method. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104, 3973,3979, 2007 [source] Onium salt reduces the inhibitory polymerization effect from an organic solvent in a model dental adhesive resinJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2008Fabrício A. Ogliari Abstract This study evaluated the effect of organic solvent concentration on the polymerization kinetics for a model dental adhesive resin containing a ternary photoinitiator system. A monomer blend based on the bis-GMA, TEGDMA, and HEMA was used as a model dental adhesive resin, which was polymerized using a binary system [camphorquinone (CQ) and ethyl 4-dimethylamine benzoate (EDAB)] and a ternary system [CQ, EDAB, and diphenyliodonium hexafluorphosphate (DPIHFP)]. Additionally, these blends had 0, 10, 20, 30, and 40 wt % ethanol added. Real-time Fourier transform infrared spectroscopy was used to investigate the polymerization reaction over photoactivation time. Data were plotted, and Hill's three-parameter nonlinear regression was performed for curve fitting. The addition of a solvent to the monomer blends decreased the polymerization kinetics, directly affecting the rate of polymerization, delaying vitrification, and attenuating the Trommsdorf effect. The introduction of DPIHFP displayed a strong increase in reaction kinetics, reducing the solvent inhibition effect. After 10 s of photoactivation, the binary system obtained in 0, 10, 20, 30, and 40% of ethanol, a degree of conversion of 44.6, 26.3, 13.4, 1.15, and 0.0%, respectively, whereas when a ternary system was used, the values were 54.6, 40.5, 27.4, 14.5, and 3.4%. An improvement was observed in the polymerization kinetics of a model dental adhesive resin when using a ternary photoinitiation system, making the material less sensitive to the residual presence of a solvent before photoactivation. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] DIATOM SILICA BIOMINERALIZATION: AT NANOSCALE LEVEL A CHEMICALLY UNIFORM PROCESSJOURNAL OF PHYCOLOGY, Issue 2000E. G. Vrieling Using a high-brilliance synchrotron X-ray source, combined small- and wide-angle X-ray scattering (SAXS and WAXS) was applied to study nanoscale characteristics, in particular pore size in the range of 3 to 65 nm, of a variety of unialgal cultures of centric and pennate diatoms, and of mixed diatom populations sampled in the field. Results of scattering analysis were compared with details of pore size, structure and orientation visible at the electron microscopic level. WAXS patterns did not reveal any crystalline phase or features of microcrystallinity (resolution 0.07 to 0.51 nm), which implies a totally amorphous character of the SiO2 matrix of the frustule material. SAXS data (resolution 3 to 65 nm) provided information on geometry, size, and distribution of pores in the silica. Overall, two pore regions were recognized that were common to the silica of all samples: the smallest (d less than 10 nm) regularly spaced and shaped spherically, the larger (up to 65 nm) being cylinders or slits. Apparently, at a nanoscale level diatomaceous silica is quite homologous among species, in agreement with the chemical principles of silica polymerization under the conditions of pH and precursor concentrations inside the silicon deposition vesicle. The final frustule "macro"-morphology is of course species-specific, being determined genetically. Synthetically-derived MCM-type silicas have a similarly organized pore distribution in an amorphous silica matrix as we found in all diatom species studied. We therefore suggest that organic molecules of a kind used as structure-directing agents to produce these artificial silicas play a role in the nucleation of the silica polymerization reaction and the shaping of pore morphology inside the silicon deposition vesicle of diatoms. Structure-directing molecules now await isolation from the SDV, followed by identification and characterisation by molecular techniques. [source] Solution, thermal and optical properties of novel poly(pyridinium salt)s derived from conjugated pyridine diamines,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2010Alexi K. Nedeltchev Abstract Several novel poly(pyridinium salt)s with heterocyclic pyridine moieties in their backbones with tosylate and triflimide counterions were prepared by either ring-transmutation polymerization reaction of phenylated-bis(pyrylium tosylate) with isomeric pyridine diamines of 4-phenyl-2,6-bis(4-aminophenyl)pyridine in dimethyl sulfoxide (DMSO) for 48 h at 130,140 °C or by metathesis reaction of the respective tosylate polymers with lithium triflimide in DMSO at about 60 °C. Their chemical structures were characterized by FTIR, 1H, 13C NMR spectroscopy, and elemental analysis. Their number-average molecular weights (Mn) were in the range of 8,000,51,000 and their polydispersities in the range of 1.18,2.13 as determined by gel permeation chromatography. They had excellent thermal stabilities of 340,458 °C and high glass transition temperatures >200 °C. As they showed good solubilities in common organic solvents, their solution properties were also characterized for their lyotropic liquid-crystalline properties with polarizing optical microscopy (POM) studies. Their photoluminescent properties were examined by using a spectrofluorometer in both solution and solid states. Their quantum yields were rather low, which were in the range of 1.3,2.0%. Additionally, hand-drawn fibers from the melts were examined to determine their morphologies with a number of microscopic techniques including POM, scanning electron microscopy, and transmission electron microscopy. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] Ethylene polymerization behavior of Cr(III)-containing montmorillonite: Influence of chromium compoundsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2009Kazuhiro Yamamoto Abstract Montmorillonite was treated with Cr(NO3)3, Cr(acetate)3, and Cr(acac)3 to give three catalyst precursors, Cr-MMT-1, Cr-MMT-2, and Cr-MMT-3, respectively. Application of these catalysts to the ethylene polymerization reaction revealed Cr-MMT-1 to be much more reactive than the other two while the molecular weight distributions of the polymers were practically the same. Elemental analysis, XRD, and TEM measurements suggested that chromium occupied the interlayer section in Cr-MMT-1 and mostly the outer surface region for the other two catalysts. Aluminosilicate-supported Cr catalysts exhibited reactivity similar to that of Cr-MMT-2 and Cr-MMT-3. However, more of the low-molecular-weight polymer was formed. These data suggested that there is a relationship between the sites of the Cr ions and catalytic reactivity, and between supporting solid identity and molecular weight distribution of the polymer. The use of n -Bu2Mg and Et2Zn in the place of Et3Al led to lower activity but gave polymers of narrower molecular weight distribution, with more of the high-molecular-weight material. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2272,2280, 2009 [source] Random poly(fluorenylene-vinylene)s containing 3,7-Dibenzothiophene-5,5-dioxide units: Synthesis, photophysical, and electroluminescence propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2009Roberto Grisorio Abstract The synthesis of new random poly(arylene-vinylene)s containing the electron withdrawing 3,7-dibenzothiophene-5,5-dioxide unit was achieved by the Suzuki,Heck cascade polymerization reaction. The properties of poly[9,9-bis(2-ethylhexyl)-2,7-fluorenylene-vinylene- co -3,7-dibenzothiophene-5,5-dioxide-vinylene] (50/50 mol/mol, P1) and poly[1,4-bis(2-ethylhexyloxy)-2,5-phenylene-vinylene- co -3,7-dibenzothiophene-5,5-dioxide-vinylene] (50/50 mol/mol, P2) were compared with those of terpolymers obtained by combining the fluorene, dibenzothiophene, and 1,4-bis(2-ethylexyloxy)benzene in 20/40/40 (P3), 50/25/25 (P4), and 80/10/10 (P5) molar ratios. The polymers were characterized by 1H NMR and IR, whereas their thermal properties were investigated by TGA and DSC. Polymers P1,5 are blue,green emitters in solution (,em between 481 and 521 nm) whereas a profound red shift observed in the solid state is emission (,em from 578 to 608 nm) that can be attributed both to the charge transfer stabilization exerted by the polar medium and to intermolecular interactions occurring in the solid state. Cyclic voltammetry permitted the evaluation of the ionization potentials and also revealed a quasi-reversible behavior in the reduction scans for the polymers (P1,4) containing the higher amounts of 3,7-dibenzothiophene-5,5-dioxide units. Electroluminescent devices with both ITO/PEDOT-PSS/P1,5/Ca/Al (Type I) and ITO/PEDOT-PSS/P1,5/Alq3/Ca/Al (Type II) configuration were fabricated showing a yellow to yellow,green emission. In the case of P4, a luminance of 1835 cd/m2 and an efficiency of 0.25 cd/A at 14 V were obtained for the Type II devices. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2093,2104, 2009 [source] Double hydrophilic block copolymers of sodium(2-sulfamate-3-carboxylate)isoprene and ethylene oxideJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2006Stergios Pispas Abstract Poly(sodium(2-sulfamate-3-carboxylate)isoprene)- b -poly(ethylene oxide) and poly(ethylene oxide)- b -poly(sodium(2-sulfamate-1-carboxylate)isoprene)- b -poly(ethylene oxide) double hydrophilic block copolymers were prepared by selective post polymerization reaction of the polyisoprene block, of poly(isoprene- b -ethylene oxide) diblocks or poly(ethylene oxide- b -isoprene- b -ethylene oxide) triblock precursors, with N -chlorosulfonyl isocyanate. The precursors were synthesized by anionic polymerization high vacuum techniques and had narrow molecular weight distributions and predictable molecular weights and compositions. The resulting double hydrophilic block copolymers were characterized by FTIR and potentiometric titrations in terms of the incorporated functional groups. Their properties in aqueous solutions were studied by viscometry and dynamic light scattering. The latter techniques revealed a complex dilute solution behavior of the novel block copolymers, resulting from the polyelectrolyte character of the functionalized PI block and showing a dependence on solution ionic strength and pH. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 606,613, 2006 [source] Side-chain terpyridine polymers through atom transfer radical polymerization and their ruthenium complexesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2005Nikos P. Tzanetos Abstract Polymers containing side-chain terpyridine ligands of well-defined architectures and controllable molecular weights and molecular weight distributions are reported. These polymers were synthesized by the atom transfer radical polymerization (ATRP) of a newly synthesized terpyridine monomer with three functional initiators. The obtained polymers were characterized with 1H NMR and gel permeation chromatography techniques. The efficiency of the ATRP technique and the overall control of the molecular characteristics of the polymers were demonstrated by a kinetic study of the polymerization reaction. Subsequently, the ruthenium(III)/ruthenium(II) complexation chemistry was employed for the attachment of bis(dodecyloxy)-functionalized terpyridine moieties onto each side 2,2,:6,,2,-terpyridine unit of the main polymeric backbone. Thus, the grafting approach was successfully combined with the metal,ligand coordination chemistry for the preparation of highly soluble polymeric complexes. The resulting complexes were fully characterized by means of 1H NMR, gel permeation chromatography, and ultraviolet,visible spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4838,4848, 2005 [source] In situ Fourier transform near infrared spectroscopy monitoring of copper mediated living radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2004Vincent Darcos Abstract In situ Fourier transform near infrared (FTNIR) spectroscopy was successfully used to monitor monomer conversion during copper mediated living radical polymerization with N -(n -propyl)-2-pyridylmethanimine as a ligand. The conversion of vinyl protons in methacrylic monomers (methyl methacrylate, butyl methacrylate, and N -hydroxysuccinimide methacrylate) to methylene protons in the polymer was monitored with an inert fiber-optic probe. The monitoring of a poly(butyl methacrylate- b -methyl methacrylate- b -butyl methacrylate) triblock copolymer has also been reported with difunctional poly(methyl methacrylate) as a macroinitiator. In all cases FTNIR results correlated excellently with those obtained by 1H NMR. On-line near infrared (NIR) measurement was found to be more accurate because it provided many more data points and avoided sampling during the polymerization reaction. It also allowed the determination of kinetic parameters with, for example, the calculation of an apparent first-order rate constant. All the results suggest that FTNIR spectroscopy is a valuable tool to assess kinetic data. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4933,4940, 2004 [source] Segmented block copolymers of poly(ethylene glycol) and poly(ethylene terephthalate)JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2004B. García-Gaitán Abstract A new series of segmented copolymers were synthesized from poly(ethylene terephthalate) (PET) oligomers and poly(ethylene glycol) (PEG) by a two-step solution polymerization reaction. PET oligomers were obtained by glycolysis depolymerization. Structural features were defined by infrared and nuclear magnetic resonance (NMR) spectroscopy. The copolymer composition was calculated via 1H NMR spectroscopy. The content of soft PEG segments was higher than that of hard PET segments. A single glass-transition temperature was detected for all the synthesized segmented copolymers. This observation was found to be independent of the initial PET-to-PEG molar ratio. The molar masses of the copolymers were determined by gel permeation chromatography (GPC). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4448,4457, 2004 [source] Effect of hydrogen-bonding interaction on radical polymerization of di- n -butyl itaconateJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2003Tomohiro Hirano Radical polymerizations of di- n -butyl itaconate (DBI) were examined in the presence of amide compounds that could form a complex with DBI monomer via a hydrogen-bonding interaction. The use of amide compounds as solvents succeeded to suppress the intramolecular chain-transfer reaction significantly, whereas catalytic amounts of amide compounds were of little effect. It was also assumed that a hydrogen-bonding interaction plays an important role not only for suppression of the intramolecular chain-transfer reaction but for stereospecificity of polymerization. These results suggested that even a weak hydrogen-bonding interaction could be used for control of a radical polymerization reaction. [source] Synthesis of hydroxy-terminated, oligomeric poly(silarylene disiloxane)s via rhodium-catalyzed dehydrogenative coupling and their use in the aminosilane,disilanol polymerization reaction,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2002Craig L. Homrighausen Abstract A series of oligomeric, hydroxy-terminated silarylene,siloxane prepolymers of various lengths were prepared via dehydrogenative coupling between 1,4-bis(dimethylsilyl)benzene [H(CH3)2SiC6H4Si(CH3)2H] and excess 1,4-bis(hydroxydimethylsilyl)benzene [HO(CH3)2SiC6H4Si(CH3)2OH] in the presence of a catalytic amount of Wilkinson's catalyst [(Ph3P)3RhCl]. Attempts to incorporate the diacetylene units via dehydrogenative coupling polymerization between 1,4-bis(dimethylsilyl)butadiyne [H(CH3)2SiCCCCSi(CH3)2H] and the hydroxy-terminated prepolymers were unsuccessful. The diacetylene units were incorporated into the polymer main chain via aminosilane,disilanol polycondensation between 1,4-bis(dimethylaminodimethylsilyl)butadiyne [(CH3)2NSi(CH3)2CCCC(CH3)2SiN(CH3)2] and the hydroxy-terminated prepolymers. Linear polymers were characterized by Fourier transform infrared, 1H and 13C NMR, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis, and they were thermally crosslinked through the diacetylene units, producing networked polymeric systems. The thermooxidative stability of the networked polymers is discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1334,1341, 2002 [source] Photoswitchable architectural polymer: Toward azo-based polyamidoamine side-chain dendritic polyesterJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2001Samaresh Ghosh Abstract A versatile approach to the synthesis of novel polyamidoamine (PAMAM) side-chain dendritic polyester (SCDPE) possessing azobenzene motifs in the polymeric core is described and displayed reversible cis,trans (E/Z) isomerization upon exposure to UV light. A polymerization reaction was conducted in solution using ester-terminated PAMAM dendritic diol (1a, G 3.5) and azobenzene dicarboxylic acid chloride in the presence of triethylamine. PAMAM dendritic diol 1a as well as SCDPE (1) were thoroughly characterized by means of IR and NMR (1H and 13C) spectroscopies. The intrinsic viscosity of 1 at 36 °C in CHCl3 was found to be 0.38 dl/g. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4182,4188, 2001 [source] Particle formation under monomer-starved conditions in the semibatch emulsion polymerization of styrene.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2001Abstract Particle formation and particle growth compete in the course of an emulsion polymerization reaction. Any variation in the rate of particle growth, therefore, will result in an opposite effect on the rate of particle formation. The particle formation in a semibatch emulsion polymerization of styrene under monomer-starved conditions was studied. The semibatch emulsion polymerization reactions were started by the monomer being fed at a low rate to a reaction vessel containing deionized water, an emulsifier, and an initiator. The number of polymer particles increased with a decreasing monomer feed rate. A much larger number of particles (within 1,2 orders of magnitude) than that generally expected from a conventional batch emulsion polymerization was obtained. The results showed a higher dependence of the number of polymer particles on the emulsifier and initiator concentrations compared with that for a batch emulsion polymerization. The size distribution of the particles was characterized by a positive skewness due to the declining rate of the growth of particles during the nucleation stage. A routine for monomer partitioning among the polymer phase, the aqueous phase, and micelles was developed. The results showed that particle formation most likely occurred under monomer-starved conditions. A small average radical number was obtained because of the formation of a large number of polymer particles, so the kinetics of the system could be explained by a zero,one system. The particle size distribution of the latexes broadened with time as a result of stochastic broadening associated with zero,one systems. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3940,3952, 2001 [source] Synthesis of poly(methyl methacrylate) in a pyridine solution by atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2001José Luis de la Fuente Abstract Pyridine was used as a solvent for the atom transfer radical polymerization (ATRP) of methyl methacrylate. The homopolymerizations were carried out with methyl 2-halopropionate (MeXPr, where X was Cl or Br) as an initiator, copper halide (CuX) as a catalyst, and 2,2,-bipyridine as a ligand from 80 to 120 °C. The mixed halogen system methyl 2-bromopropionate/copper chloride was also used. For all the initiator systems used, the polymerization reaction showed linear first-order rate plots, a linear increase in the number-average molecular weight with conversion, and relatively low polydispersities. In addition, the dependence of the polymerization rate on the temperature is presented. These data are compared with those obtained in bulk, demonstrating the effectiveness of this solvent for this monomer in ATRP. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3443,3450, 2001 [source] Preparation and characterization of polymethacrylate monolithic capillary columns with dual hydrophilic interaction reversed-phase retention mechanism for polar compoundsJOURNAL OF SEPARATION SCIENCE, JSS, Issue 15-16 2009í Urban Abstract Monolithic columns for capillary hydrophilic interaction liquid chromatography (HILIC) were prepared in fused-silica capillaries by radical co-polymerization of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide and ethylene dimethacrylate in various binary and ternary porogen solvent mixtures with azobisisobutyronitrile as the initiator of the polymerization reaction. Columns showed mixed separation modes: reversed-phase (RP) in water-rich mobile phases and HILIC at high concentrations of acetonitrile (>60,80%) in aqueous,organic mobile phases. A continuous change in retention was observed at increasing concentration of water in acetonitrile, giving rise to characteristic U-turn plots of retention factors versus the concentration of water in the mobile phase, with minima corresponding to the transition between the mechanisms controlling the retention. The selectivity of organic polymer monolithic columns for HILIC separations can be varied by adjusting the concentration of sulfobetaine monomer and the composition of the porogen solvent in the polymerization mixture. Under HILIC conditions, the monolithic capillary sulfobetaine columns show separation selectivities for polar phenolic acids similar to those of a commercial silica-based sulfobetaine ZIC-HILIC column, which, however, has limited selectivity in the RP mode due to lower retention. [source] New agitated and thermostatized cell for in situ monitoring of fast reactions by synchrotron SAXSJOURNAL OF SYNCHROTRON RADIATION, Issue 6 2009Maria Paulis A thermostatized and agitated sample cell for synchrotron small-angle X-ray scattering (SAXS) measurements of liquid samples (homogeneous or heterogeneous) has been developed. The cell is composed of a compact main body with inlet and outlet windows for the beams of light. The volume of the cell is approximately 0.8,ml and the distance between the windows is 5,mm to allow accurate SAXS measurements. The cell is thermostatized by means of a jacket that surrounds the sample holder and it is connected to a thermostatic bath. In addition, the cell has a top and a bottom lid that allow easy cleaning and maintenance without demounting the optical windows. The cell has been used to run SAXS measurements of liquid samples and, for the first time, a mini-emulsion polymerization reaction has been monitored by SAXS. [source] Using Differential Scanning Calorimetry to Follow How Gelcasting ProceedsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2007BoonSing Ng Differential scanning calorimetry studies on aqueous low-toxicity monomer,crosslinker gelcasting systems loaded with zirconia powder provided information on the onset and kinetics of the polymerization reaction. A simple procedure was developed to determine the relative importance of the individual components on the gelation process. It was found that the thermal stability and dissociation of the initiator control the gelation rate and that the zirconia particles accelerate the gelation. [source] AB2 Functional Polyesters via Ring Opening Polymerization: Synthesis and CharacterizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 8 2009Ingrid W. Velthoen Abstract Aliphatic AB2 functional polyesters were conveniently prepared by the ring opening polymerization of , -caprolactone and L -lactide in the presence of the AB2 functional initiator 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) and Sn(Oct)2 as the catalyst. In L -lactide polymerization, both bis-MPA hydroxyl groups initiated the polymerization reaction, but for , -caprolactone polymerization this depended on the monomer to initiator to catalyst ratio. Initiation at two hydroxyl groups occurred at high monomer to initiator ([M]/[I]) ratio and at high Sn(Oct)2 to monomer ratio. The melting temperatures of the AB2 -functional PLLA and PCL polymers were comparable to linear polymers with a equal to the per arm in the polymer. [source] Tandem Action of TpMsNiCl and Supported Cp2ZrCl2 Catalysts for the Production of Linear Low-Density PolyethyleneMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 9 2006Maria Cristina A. Kuhn Abstract Summary: Linear low-density polyethylene (LLDPE) samples with different properties were prepared from ethylene, without the addition of an , -olefin co-monomer, using a combination of the catalyst precursors TpMsNiCl (TpMs,=,hydridotris(3-mesitylpyrazol-1-yl) and Cp2ZrCl2/SMAO-4, by varying the nickel loading mole fraction (xNi). Upon activation with methylaluminoxane (MAO), this binary catalytic system showed activities varying from 12.3 to 309.1 kg of PE,·,(mol[M],·,atm,·,h),1. The properties of the polymeric materials are influenced by xNi as well as by the temperature of polymerization, affording the copolymers with a melting point (Tm) between 118 and 135,°C. The GPC results show that the molecular weight () of the polymers is sensitive to the xNi. In all of the cases studied, the GPC curves displayed monomodal molecular weight distributions (MWDs) with the average molecular weight varying from 30,000 to 507,000 g,·,mol,1. Studies using dynamic mechanical thermal analysis (DMTA) show that the formation of different polymeric materials is associated with the branching content, with the stiffness varying according to the xNi and the temperature used in the polymerization reaction. Overview of the copolymerization process, from ethylene in the presence of MAO, mediated by catalysts 1 and 2/SMAO. [source] Metallocene Combinations in Ethylene Polymerization: A Cyclic and Differential Pulse Voltammetry StudyMACROMOLECULAR REACTION ENGINEERING, Issue 3 2008Fernando Silveira Abstract A series of metallocenes, namely [Cp2ZrCl2], [(MeCp)2ZrCl2], [(nBuCp)2ZrCl2], [(iBuCp)2ZrCl2], [(tBuCp)2ZrCl2], [Cp2TiCl2], [Et(Ind)2ZrCl2], [Et(IndH4)2ZrCl2] and [MeSi2(Ind)2ZrCl2)], were combined in a 1:1 molar ratio within a reactor for ethylene polymerization, with MAO as the cocatalyst. The catalysts were characterized by cyclic and differential pulse voltammetry. The combined systems that showed the highest and lowest activities were combined in 1:3 and 3:1 molar ratios. The catalyst activity in the ethylene polymerization reaction is discussed in terms of the estimated consumption rate, decomposition rate constant and half-life of the metallocene species formed with MAO in an ethylene atmosphere. [source] Effect of bifunctional modifiers of the clay on the morphology of novolac cured epoxy resin/clay nanocompositesPOLYMER COMPOSITES, Issue 10 2008Tsung-Yen Tsai Montmorillonite type clay, (PK-802) is modified by the bifunctional modifiers (2-phenylimidazole/benzalkonium chloride, PI/BEN or 2-methylimidazole/benzalkonium chloride, MI/BEN) with different ratio, which contain a curing agent, BEN, and the promoters/accelerator (PI and MI). These two modifying agents are simultaneously intercalated into the gallery space of pure PK-802. The novolac cured epoxy nanocomposites are prepared with this modified clay by crosslinking polymerization reaction. Wide-angle X-ray diffraction is used to measure the resulting d -spacing of modified PK-802 and the nanocomposites. Thermo-gravimetric analysis is used to characterize the thermal properties of the nanocomposites. The morphology of the nanocomposites is investigated using transmission electron microscopy techniques. Well dispersion of clay into the novolac cured epoxy-clay nanocomposites resulted when simultaneously both the modifying agents with 5:5 mole ratios are used to modify the clay instead of using single modified agent. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers [source] Polymerization compounding of HDPE/Kevlar composites.POLYMER COMPOSITES, Issue 2 2006The aim of this work is to perform the polymerization compounding to improve the properties of Kevlar/PE composites. The approach consists in involving the surface of a reinforcement in a polymerization process of a polymer to be used either as a matrix in the final composite or as a special surface treatment to enhance solid/polymer interface properties in the composite. The polymerization compounding process is illustrated here with the polyaramid fibers as reinforcements and polyethylene as a matrix. The number of active sites on the fiber surface, initially insufficient to anchor the catalyst, were increased by a hydrolysis reaction prior to the polymerization. The anchored catalyst was subsequently used to conduct the Ziegler,Natta polymerization reaction of ethylene. The modified fibers were incorporated into the polyethylene resin to produce composites at fiber concentrations as high as 15 wt%. The morphology of the fibers and the composites was tested using electron microscopy. Finally, the mechanical properties of the composites (in impact and tensile tests) were measured to characterize the properties of model composites. Polym. Compos. 27:129,137, 2006. © 2006 Society of Plastics Engineers. [source] Multiobjective optimization of polymerization reaction of vinyl acetate by genetic algorithm technique with a new replacement criterionPOLYMER ENGINEERING & SCIENCE, Issue 5 2008Maryam Sadi A multiobjective optimization procedure based on genetic algorithm has been developed to determine optimum operational conditions of polymerization reaction. In this article by using a new selection criterion to choose the next generation members with better quality, optimization efficiency is improved and the number of generations to obtain Pareto optimal set reduced. In this proposed method a novel replacement criterion based on ranking level information and proximity of solutions to the Pareto optimal front is used to choose the next generation members. The polymerization of vinyl acetate has been chosen as an example. Two objective functions, which used in this study, are maximization of the weight average molecular weight up to the desired value and minimization of the residual initiator concentration. A Pareto optimal set of objective functions has been obtained by application of a Pareto set filter operator. Furthermore, the influence of genetic algorithm parameters on the efficiency and convergence of genetic algorithm is studied by changing cross over and mutation probabilities. Because of the flexibility and generality of genetic algorithm, this optimization method is a useful technique with lots of potentials in determination of optimum value of operation parameters. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers [source] Synthesis and characterization of polyaniline derivative and silver nanoparticle compositesPOLYMER INTERNATIONAL, Issue 10 2008Gururaj M Neelgund Abstract BACKGROUND: There has been a recent surge of interest in the synthesis and applications of electroactive polymers with incorporated metal nanoparticles. These hybrid systems are expected to display synergistic properties between the conjugated polymers and the metal nanoparticles, making them potential candidates for applications in sensors and electronic devices. RESULTS: Composites of polyaniline derivatives,polyaniline, poly(2,5-dimethoxyaniline) and poly(aniline-2,5-dimethoxyaniline),and silver nanoparticles were prepared through simultaneous polymerization of aniline derivative and reduction of AgNO3 in the presence of poly(styrene sulfonic acid) (PSS). We used AgNO3 as one of the initial components (1) to form the silver nanoparticles and (2) as an oxidizing agent for initiation of the polymerization reaction. UV-visible spectra of the synthesized nanocomposites reveal the synchronized formation of silver nanoparticles and polymer matrix. The morphology of the silver nanoparticles and degree of their dispersion in the nanocomposites were characterized by transmission electron microscopy. Thermogravimetric analysis and differential scanning calorimetry results indicate an enhancement of the thermal stability of the nanocomposites compared to the pure polymers. The electrical conductivity of the nanocomposites is in the range 10,4 to 10,2 S cm,1. CONCLUSION: A single-step process for the synthesis of silver nanoparticle,polyaniline derivative nanocomposites doped with PSS has been demonstrated. The approach in which silver nanoparticles are formed simultaneously during the polymerization process results in a good dispersion of the nanoparticles in the conductive polymer matrix. Copyright © 2008 Society of Chemical Industry [source] | ||||||||||||||||