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Radical Copolymerization (radical + copolymerization)
Kinds of Radical Copolymerization Selected AbstractsGelation and Hollow Particle Formation in Nitroxide-Mediated Radical Copolymerization of Styrene and Divinylbenzene in MiniemulsionMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2009Per B. Zetterlund Abstract Network formation in the nitroxide-mediated cross-linking copolymerization of styrene and divinylbenzene (3 or 8.2 mol-% relative to total monomer) using the nitroxide 2,2,6,6-tetramethylpiperidinyl-1-oxy (TEMPO) at 125,°C can proceed markedly differently in aqueous miniemulsion compared to the corresponding solution polymerization depending on the organic-phase composition. When the organic phase comprises 54 vol-% of the hydrophobe tetradecane, gelation occurs at much lower conversion in miniemulsion than in solution, and at significantly lower conversion than predicted by Flory,Stockmayer gelation theory. This is proposed to be a result of an effect of the oil,water interface, whereby the concentration of polymer with pendant unsaturations is higher near the interface than in the particle interior. [source] One-Pot Approach to Synthesize Star-Shaped Polystyrenes via RAFT-Mediated Radical CopolymerizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 22 2007Qingchun Liu Abstract Previously, we have reported a one-pot approach to generate star-shaped polymers by copolymerization of a maleimide inimer or bismaleimide hexane (BMIH) and a large excess of styrene (St) via atom transfer radical polymerization. Herein, we extended this approach towards the synthesis of star polystyrene through reversible addition fragmentation chain-transfer (RAFT)-mediated radical copolymerization of BMIH and an excess of St with cumyl dithiobenzoate (CDB) as a chain-transfer agent (CTA). It was illustrated that the PS arms were grafted from the preformed core, which was formed in situ during the copolymerization of BMIH and St. Therefore, this facile one-pot approach can be performed by applying different type of controlled radical polymerization. However, linear PS still was generated as a byproduct which had been observed previously. [source] N -Oxyl-Controlled Radical Copolymerization of Styrene with Ethyl , -CyanocinnamateMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 11 2004Andreas Bartsch Abstract Summary: The block copolymers of styrene and ethyl , -cyanocinnamate were prepared in dioxane and xylene with TEMPO-capped polystyrene (PSTEMPO) as macroinitiator. The copolymerizations were carried out at 125,°C and 135,°C. The reactivity ratios were determined according to Kelen Tüdos and compared with the reactivity ratios from the radical copolymerization of styrene and ethyl , -cyanocinnamate determined by Kohn et al. The influence of the comonomer ethyl , -cyanocinnamate on the glass transition temperature was studied in comparison with the corresponding homopolystyrene. Plots of conversion versus molecular weight distributions of the polymerizations with styrene at 125,°C. [source] Modeling of the Nitroxide-Mediated Radical Copolymerization of Styrene and DivinylbenzeneMACROMOLECULAR REACTION ENGINEERING, Issue 5-6 2009Julio C. Hernández-Ortiz Abstract A mathematical model for the copolymerization kinetics with crosslinking of vinyl/divinyl monomers in the presence of nitroxide controllers has been developed and validated using experimental data of TEMPO-mediated copolymerization of styrene (STY) and divinylbenzene (DVB). Polymerization rate, molecular weight development, gelation point, evolution of sol and gel weight fractions, crosslink density, and copolymer composition, as well as concentrations of the species participating in the reaction mechanism can be calculated with the model. Diffusion-controlled effects were assessed and found unimportant. The presence of nitroxide controllers seems to favor the production of more homogeneous polymer networks, but this effect decreases as the initial fraction of crosslinker is increased. [source] Mathematical Modeling of Atom-Transfer Radical CopolymerizationMACROMOLECULAR REACTION ENGINEERING, Issue 4 2007Mamdouh Al-Harthi Abstract A comprehensive mathematical model for atom transfer radical copolymerization in a batch reactor is presented using the concept of pseudo-kinetic rate constants and the method of moments. The model describes molecular weight, monomer conversion, polydispersity index, and copolymer composition as a function of polymerization time. Model predictions were compared with experimental data for styrene and butyl acrylate copolymerization and excellent agreement was obtained. We have also tested the model with styrene-acrylonitrile copolymerization data obtained in our laboratory. Finally, we used the model to study the effect of comonomer reactivity ratio, feed composition, activation and deactivation rate constants on the copolymer composition. [source] Comprehensive Study of Free Radical Copolymerization Using a Monte Carlo Simulation Method, 1MACROMOLECULAR THEORY AND SIMULATIONS, Issue 5 2005Yousef Mohammadi Abstract Summary: In order to investigate the influence of reactivity ratios and initial feed composition on the microstructure of macromolecules in free radical copolymerization, a comprehensive study was carried out using a Monte Carlo simulation method. As a result, a new procedure was introduced to modify the works of others on the initiation step. The variation of the copolymer composition and the fashion of the arrangement of monomers in simulated chains were evaluated as a function of copolymerization parameters. The model was capable of monitoring any change in azeotropy as well as the magnitude and direction of composition drift from the azeotrope point. The maximum reachable conversion (MRC) was predicted for different combinations of initial feed compositions and reactivity ratios. According to the simulation results, a critical conversion where the macromolecules produced inherited the maximum allowed alternation was obtained for the reactivity ratios given. Change of sequence distribution of simulated copolymer chains with conversion for various initial feed compositions on a triangular graph (rA,=,0.5, rB,=,0.9). [source] Thin semitransparent gels containing phenylboronic acid: porosity, optical response and permeability for sugarsJOURNAL OF MOLECULAR RECOGNITION, Issue 2 2008Alexander E. Ivanov Abstract Radical copolymerization of acrylamide (Am) (90,mol%) with N -acryloyl- m -aminophenylboronic acid (NAAPBA) (10,mol%) carried out on the surface of glass slides in aqueous solution and in the absence of chemical cross-linkers, resulted in the formation of thin semitransparent gels. The phenylboronic acid (PBA) ligand density was ca. 160,µmol/ml gel. The gels exhibited a macroporous structure and displayed optical response to sucrose, lactose, glucose and fructose in 50,mM sodium phosphate buffer, in the pH range from 6.5 to 7.5. The response was fairly reversible and linearly depended on glucose concentration in the wide concentration range from 1 to 60,mM at pH 7.3. The character of response was explained by the balance of two competing equilibrium processes: binding of glucose to phenylboronate anions and binary hydrophobic interactions of neutral PBA groups. The apparent diffusion coefficient of glucose in the gels was ca. 2.5,×,10,7,cm2/s. A freshly prepared gel can be used daily for at least 1 month without changes in sensitivity. Autoclaving (121°C, 1.2 bar, 10,min) allows for the gels sterilization, which is important for their use as glucose sensors in fermentation processes. Copyright © 2008 John Wiley & Sons, Ltd. [source] Radical copolymerization of vinylidene cyanide with 2,2,2-trifluoroethyl methacrylate: Structure and characterization,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2010Mustapha Raihane Abstract A novel copolymer of vinylidene cyanide (VCN) and 2,2,2-trifluoroethyl methacrylate (MATRIF) was synthesized by bulk free radical process in a 52% yield from an equimolar comonomer feed. The copolymer's composition and microstructure were analyzed by FTIR, 1H- and 13C-NMR spectroscopy, SEC, and elemental analysis. The reactivity ratios calculated from both the Q-e Alfrey-Price parameters and the Jenkins' Patterns Scheme indicate a tendency to alternation in the copolymerization, the latter method suggesting that MATRIF homopropagation be slightly favoured (rV = r12 = 0.1, rM = r21 = 0.3). The molar incorporation of VCN in the copolymer was only 42 mol % according to the 9.0 wt % nitrogen content determined by elemental analysis, in good agreement with the value obtained by 1H-NMR. High-resolution 1H and 13C-NMR spectra were used to study the microstructure of the copolymer. As an example, the three well-resolved carbonyl resonances in the 13C-NMR spectrum were assigned to the MATRIF-centered triads VMV, VMM, and MMM, respectively, (V and M stand for VCN and MATRIF, respectively). The presence of VCN dyads (e.g., in VVM and VVV sequences) was shown to be marginal or absent altogether. Thermogravimetric analysis of poly(VCN- co -MATRIF) copolymer showed good thermal stability, and its main pyrolytic degradation taking place only above 368 °C. A 4% weight loss at about 222 °C suggested the presence of a few VCN homodyads, possibly inducing thermal depolymerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] Radical copolymerization of vinylidene fluoride with 1-bromo-2,2-difluoroethyleneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2010G. K. Kostov Abstract The radical copolymerization of vinylidene fluoride (VDF) and 1-bromo-2,2-difluoroethylene (BDFE) in 1,1,1,3,3-pentafluorobutane solution at different monomer molar ratios (ranging from 96/4 to 25/75 mol %) and initiated by tert -butylperoxypivalate (TBPPI, mainly) is presented. Poly(VDF- co -BDFE) copolymers of various aspects (from white powders to yellow viscous liquids) were produced depending on the copolymer compositions. The microstructures of the obtained copolymers were characterized by 19F and 1H NMR spectroscopy and by elementary analysis and these techniques enabled one to assess the contents of both comonomers in the produced copolymers. VDF was shown to be more incorporated in the copolymer than BDFE. From the extended Kelen and Tudos method, the kinetics of the radical copolymerization led to the determination of the reactivity ratios, ri, of both comonomers (rVDF = 1.20 ± 0.50 and rBDFE = 0.40 ± 0.15 at 75 °C) showing that VDF is more reactive than BDFE. Alfrey-Price's Q and e values of BDFE monomer were calculated to be 0.009 (from QVDF = 0.008) or 0.019 (from QVDF = 0.015) and +1.22 (vs. eVDF = 0.40) or +1.37 (vs. eVDF = 0.50), respectively, indicating that BDFE is an electron-accepting monomer. Statistic cooligomers were produced with molar masses ranging from 1,800 to 5,500 g/mol (assessed by GPC with polystyrene standards). A further evidence of the successful copolymerization was shown by the selective reduction of bromine atoms in poly(VDF- co -BDFE) cooligomers that led to analog PVDF. The thermal properties of the poly(VDF- co -BDFE) cooligomers were also determined and those containing a high VDF amount exhibited a high thermal stability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3964,3976, 2010. [source] Radical polymerization behavior of ethyl ortho -(4-phenyl-1,3-dioxolan-2-yl)phenyl fumarateJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2002Makiko Seno Abstract The polymerization of ethyl ortho -(4-phenyl-1,3-dioxolan-2-yl)phenyl fumarate (EPDPF) with dimethyl 2,2,-azobisisobutyrate (MAIB) was kinetically investigated in benzene. The polymerization rate (Rp) at 60 °C was presented by Rp = k[MAIB]1.1[EPDPF]0.8. The number-average molecular weight of poly(EPDPF) was in the range of 2500,3500. Analysis of 1H and 13C NMR spectra of the resulting polymers suggested that the radical polymerization of EPDPF proceeds in a complicated manner involving vinyl addition, intramolecular hydrogen abstraction, and ring opening of the cyclic acetal. The polymerization system involved electron spin resonance (ESR)-observable poly(EPDPF) radicals under the practical polymerization conditions. ESR-determined apparent rate constants (2.0,8.5 L/mol s) of propagation increased with increasing initiator concentration and decreasing monomer concentration. The apparent rate constants (0.68,6.6 × l06 L/mol s) of termination decreased with the monomer concentration and slightly increased with the initiator concentration. The activation energies of initiation (Ei), propagation (Ep), and termination (Et) were calculated as Ei = 158, Ep = 41, and Et = 30 kJ/mol, respectively. Radical copolymerization of EPDPF with styrene was also examined at 70 °C in benzene. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2945,2955, 2002 [source] Novel amphiphilic polymer gel electrolytes based on (PEG- b -GMA)- co -MMAJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010Dan Luo Abstract Amphiphilic conetwork,structured copolymers containing different lengths of ethylene oxide (EO) chains as ionophilic units and methyl methacrylate (MMA) chains as ionophobic units were prepared by free radical copolymerization and characterized by FTIR and thermal analysis. Polymer gel electrolytes based on the copolymers complexed with liquid lithium electrolytes (dimethyl carbonate (DMC) : diethyl carbonate (DEC) : ethylene carbonate (EC) = 1 : 1 : 1 (W/W/W), LiPF6 1.0M) were characterized by differential scanning calorimetry and impedance spectroscopy. A maximum ion conductivity of 4.27 × 10,4 S/cm at 25oC was found for the polymer electrolyte based on (PEG2000- b -GMA)- co -MMA with long EO groups. Moreover, the effect of temperature on conductivity of the amphiphilic polymer electrolytes obeys the Arrhenius equation. The good room temperature conductivity of the polymer electrolytes is proposed to relate to the enhancement in the amorphous domain of the copolymers due to their amphiphilic conetwork structure. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Properties of a poly(acrylamide- co -diallyl dimethyl ammonium chloride) hydrogel synthesized in a water,ionic liquid binary systemJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Qian Zhao Abstract A novel copolymer hydrogel, poly(acrylamide- co -diallyl dimethyl ammonium chloride), was prepared by the radical copolymerization of acrylamide and diallyl dimethyl ammonium chloride in an ionic liquid (IL),water binary system in the presence of the crosslinker N,N,-methylene bisacrylamide. The equilibrium swelling ratios of the hydrogels synthesized in the IL,water binary system increased with the content of IL and were remarkably higher than that of the gel synthesized in water. Differential scanning calorimetry measurements showed that the glass-transition temperatures of the dry hydrogels that were synthesized in the IL,water binary system were remarkably lower than that of the gel synthesized in pure water. The mechanical properties of the gels synthesized in both water and the IL,water binary system were characterized with a universal material-testing machine. The results show that fracture toughness of the hydrogels was improved when they were synthesized in the IL,water binary system. The gel shrank under a direct-current electric field. The response rates of the gels that were synthesized with the IL,water binary system were faster than that of the gel synthesized in water. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Kinetics and mechanism of the radical copolymerization of 4-vinyl pyridine with methyl acrylate initiated by p -acetylbenzylidene triphenylarsonium ylideJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2009S. P. Tiwari Abstract The free-radical copolymerization of 4-vinyl pyridine (4-VP) with methyl acrylate (MA) initiated by p -acetylbenzylidene triphenylarsonium ylide at 60 ± 0.1°C with dioxane as an inert solvent yielded random copolymers. The kinetic equation was Rp , [Ylide]0.83[4-VP]0.33 [MA]0.40 (where Rp is the rate of polymerization); in other words, the system followed nonideal kinetics. The values of the energy of activation and kp2/kt (where kp is the rate constant of propagation and kt is the rate constant of termination) were 23.21 kJ/mol and 1.212 × 10,5 mol L,1 s,1, respectively. The reactivity ratios calculated with the Kelen,Tüdos method were 0.14 ± 0.0075 for 4-VP and 0.56 ± 0.0078 for MA. The copolymers were characterized with Fourier transform infrared, proton nuclear magnetic resonance, differential scanning calorimetry, and electron spin resonance methods. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source] Graft copolymers of methyl methacrylate and poly([R]-3-hydroxybutyrate) macromonomers as candidates for inclusion in acrylic bone cement formulations: Compression testingJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2006Sophie Nguyen Abstract Graft copolymers of methyl methacrylate and biodegradable, biocompatible bacterial poly([R]-3-hydroxybutyrate) (PHB) blocks were synthesized and evaluated as possible constituents in acrylic bone cements for use in orthopaedic applications. The copolymers were produced by conventional free radical copolymerization and incorporated in one commercially available acrylic bone cement brand, Antibiotic Simplex® (AKZ). Cements with formulations containing 6.7 and 13.5 wt % of PMMA- graft -PHB were prepared. The morphology of the graft copolymer particles was suggested to influence the ability of the modified cement to be processed. Formulations containing more than about 20 wt % of the graft copolymer resulted in cement doughs that, both after first preparation and several hours later, were either sandy or soft spongy in texture and, thus, would be unacceptable for use in orthopaedic applications. The morphologies of the powders and the volumetric porosity (p) and ultimate compressive strength (UCS) of the cured cements were determined. Micro computed tomography showed that the cements presented average porosities of 13.5,16.9%. It was found that, while the powder particle shape and size for the experimental cements were markedly different from those of AKZ, there was no significant difference in either p or UCS for these cements. The latter was determined to be about 85 MPa for the modified cements and 84 MPa for Antibiotic Simplex. Furthermore, the UCS of all the cements exceeded the minimum level for acrylic bone cements, as stipulated by ASTM F-451. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2006 [source] Semibatch RAFT polymerization for producing ST/BA copolymers with controlled gradient composition profilesAICHE JOURNAL, Issue 4 2008Xiaoying Sun Abstract With controlled/living radical copolymerization, the composition profile along polymer chains becomes a tunable parameter in preparing copolymer products for novel materials properties. In this work, a novel series of styrene/butyl acrylate (St/BA) copolymers with precisely designed composition profiles (uniform, linear gradient, tanh gradient, and triblock with a linear gradient mid-block) were produced using a semibatch reversible addition-fragmentation chain transfer copolymerization mediated by benzyl dithioisobutyrate. The comonomer feeding rate was programmed based on a kinetic model with the targeted composition profile as an objective functions. The experimental composition and molecular weight profiles agreed very well with the model predictions. The polymer molecular weight distributions were narrow with polydispersity index values about 1.3. The amount of dead chains was controlled below 10%. The glass transition behaviors of the St/BA copolymers were evaluated and their Tg values were found to be in an order of uniform < linear gradient < tanh gradient < triblock with 10°C for uniform and 140°C for triblock copolymers. © 2008 American Institute of Chemical Engineers AIChE J 2008 [source] Synthesis and properties of methacrylate-based networked polymers having ionic liquid structuresJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2010Kozo Matsumoto Abstract Methacrylate-based networked polymers having ionic liquid structures were prepared by radical copolymerization of methyl methacrylate (MMA) with multifunctional crosslinkers: ethyleneglycol dimethacrylate (EGDMA), trimethylolpropane trimethacrylate (TMPTMA), or triethyleneglycol dimethacrylate (TEGDMA), in the presence of 1-ethyl-3-methylethyl-1-imidazolium bis(trifluoromethane)sulfonyl imide (EMImTFSI). The fundamental physical properties of several film samples prepared by varying the monomer composition and ionic liquid content were investigated. The obtained materials became turbid with increasing crosslinker content and ionic liquid content. Their ionic conductivity increased with increasing ionic liquid content, while it was almost independent of the crosslinker content. EGDMA-derived materials and TMPTMA-derived materials showed higher ionic conductivity than TEGDMA-derived materials. TMPTMA-derived materials showed higher thermal stability than EGDMA or TEGDMA-derived materials. EGDMA and TMPTMA-derived materials were stiffer than the TEGDMA-derived materials. The elastic modulus of the film samples increased but the film became more brittle with the increase of crosslinker content. Scanning electron microscopy and atomic force microscopy observation revealed that phase separation of networked polymers and ionic liquid occurred in the highly crosslinked samples, and the phase separation structures became larger in scale with the increase of crosslinking density. This phase separation was considered to have a strong effect on the mechanical properties of the film samples. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010 [source] Radical copolymerization of vinylidene fluoride with 1-bromo-2,2-difluoroethyleneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2010G. K. Kostov Abstract The radical copolymerization of vinylidene fluoride (VDF) and 1-bromo-2,2-difluoroethylene (BDFE) in 1,1,1,3,3-pentafluorobutane solution at different monomer molar ratios (ranging from 96/4 to 25/75 mol %) and initiated by tert -butylperoxypivalate (TBPPI, mainly) is presented. Poly(VDF- co -BDFE) copolymers of various aspects (from white powders to yellow viscous liquids) were produced depending on the copolymer compositions. The microstructures of the obtained copolymers were characterized by 19F and 1H NMR spectroscopy and by elementary analysis and these techniques enabled one to assess the contents of both comonomers in the produced copolymers. VDF was shown to be more incorporated in the copolymer than BDFE. From the extended Kelen and Tudos method, the kinetics of the radical copolymerization led to the determination of the reactivity ratios, ri, of both comonomers (rVDF = 1.20 ± 0.50 and rBDFE = 0.40 ± 0.15 at 75 °C) showing that VDF is more reactive than BDFE. Alfrey-Price's Q and e values of BDFE monomer were calculated to be 0.009 (from QVDF = 0.008) or 0.019 (from QVDF = 0.015) and +1.22 (vs. eVDF = 0.40) or +1.37 (vs. eVDF = 0.50), respectively, indicating that BDFE is an electron-accepting monomer. Statistic cooligomers were produced with molar masses ranging from 1,800 to 5,500 g/mol (assessed by GPC with polystyrene standards). A further evidence of the successful copolymerization was shown by the selective reduction of bromine atoms in poly(VDF- co -BDFE) cooligomers that led to analog PVDF. The thermal properties of the poly(VDF- co -BDFE) cooligomers were also determined and those containing a high VDF amount exhibited a high thermal stability. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3964,3976, 2010. [source] Synthesis of oily core-hybrid shell nanocapsules through interfacial free radical copolymerization in miniemulsion: Droplet formation and nucleationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2010Z. H. Cao Abstract Nanocapsules with an oily core and an organic/inorganic hybrid shell were elaborated by miniemulsion (co)polymerization of styrene, divinylbenzene, ,-methacryloyloxy propyl trimethoxysilane, and N -isopropyl acrylamide. The hybrid copolymer shell membrane was formed by polymerization-induced phase separation at the interface of the oily nanodroplets with water. It was shown that the size, size distribution, and colloidal stability of the miniemulsion droplets were extremely dependent on the nature of the oil phase, the monomer content and the surfactant concentration. The less water-soluble the hydrocarbon template and the higher the monomer content, the better the droplet stability. The successful formation of nanocapsules with the targeted core-shell morphology (i.e., a liquid core surrounded by a solid shell) was evidenced by cryogenic transmission electron microscopy. Both nanocapsules and nanoparticles were produced by polymerization of the miniemulsion droplets. The proportion of nanoparticles increased with increasing monomer concentration in the oil phase. These undesirable nanoparticles were presumably formed by homogeneous nucleation as we showed that micellar nucleation could be neglected under our experimental conditions even for high surfactant concentrations. The introduction of ,-methacryloyloxy propyl trimethoxysilane was considered to be the main reason for homogeneous nucleation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 593,603, 2010 [source] Magnetic field effects on the copolymerization of water-soluble and ionic monomersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2009Ignacio Rintoul Abstract The effect of magnetic field (MF) on the radical copolymerization of a series of water-soluble and ionic monomers is presented including acrylamide (AM), acrylic acid (AA), its ionized form acrylate (A,), and diallyldimethylammonium chloride (DADMAC). The following combinations have been studied: AM/AA, AM/A,, AM/DADMAC, and AA/DADMAC. In addition to the MF, strong electrostatic interactions are present for the majority of monomer combinations and conditions. Although the monomer consumption rate (Rp) increased up to 65% applying a MF of 0.1 Tesla, the composition of the resulting copolymers was not affected under such conditions. Despite this increase of Rp by MF, the electrostatic repulsion between ionic monomers and charged growing radicals dominates Rp and governs the copolymer composition with and without MF. The order of the experimentally obtained reactivity ratios reflects the extent of electrostatic interaction: rAM/AA (1.41) < r (3.10) < rAA/DADMAC (4.25) < rAM/DADMAC (6.95) and rAA/AM (2.20) > rDADMAC/AA (0.25) > r (0.17) > rDADMAC/AM (0.03). Overall, weak MF offers to reduce the production time without modifying the product composition. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 373,383, 2009 [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 poly[N -isopropylacrylamide- g -poly(ethylene glycol)] with a reactive group at the poly(ethylene glycol) end and its thermosensitive self-assembling characterJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2006Michihiro Iijima Abstract Poly[N -isopropylacrylamide- g -poly(ethylene glycol)]s with a reactive group at the poly(ethylene glycol) (PEG) end were synthesized by the radical copolymerization of N -isopropylacrylamide with a PEG macromonomer having an acetal group at one end and a methacryloyl group at the other chain end. The temperature dependence of the aqueous solutions of the obtained graft copolymers was estimated by light scattering measurements. The intensity of the light scattering from aqueous polymer solutions increased with increasing temperature. In particular, at temperatures above 40°C, the intensity abruptly increased, indicating a phase separation of the graft copolymer due to the lower critical solution temperature (LCST) of the poly(N -isopropylacrylamide) segment. No turbidity was observed even above the LCST, and this suggested a nanoscale self-assembling structure of the graft copolymer. The dynamic light scattering measurements confirmed that the size of the aggregate was in the range of several tens of nanometers. The acetal group at the end of the PEG graft chain was easily converted to the aldehyde group by an acid treatment, which was analyzed by 1H NMR. Such a temperature-induced nanosphere possessing reactive PEG tethered chains on the surface is promising for new nanobased biomedical materials. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1457,1469, 2006 [source] Copolymerization of vinylidene difluoride with hexafluoropropene in supercritical carbon dioxideJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2006Uwe Beginn Abstract Vinylidene difluoride and hexafluoropropene are copolymerized in supercritical carbon dioxide at 280 bar and 50 °C by means of free radical copolymerization, initiated by diethyl peroxydicarbonate. The first stages of the reaction were monitored by turbidity measurements and the time/conversion curve was followed gravimetrically to measure the initial rates of polymerization. The obtained copolymers possessed bimodal molecular weight distributions, their average comonomer composition was well described by the Lewis-Mayo equation with the copolymerization parameters rVDF = 4.8 and rHFP = 0. The glass transition and melting temperatures of the copolymers are similar to that of the materials resulting from aqueous emulsion polymerization. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1299,1316, 2006 [source] Interfacial living radical copolymerization of oil- and water-soluble comonomers to form composite polymer capsulesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2006Mir Mukkaram Ali Abstract The suspension copolymerization of methyl methacrylate with hydroxy-functional poly(ethylene glycol) monomethacrylate (PEGMA) by atom transfer radical polymerization (ATRP) yielded soluble, controlled-molecular-weight amphiphilic copolymers (weight-average molecular weight/number-average molecular weight <1.3). Despite extensive partitioning of PEGMA into the water phase, copolymers containing up to 24 mol % PEGMA were formed in the oil phase, from comonomer feeds containing 30 mol % PEGMA. Conversions by suspension polymerization were comparable to those obtained by solution polymerization, at over 70%. Suspension copolymers with high PEGMA contents contained high-molecular-weight polymer formed by uncontrolled polymerization, unless poly(vinyl pyrrolidone) was added to displace the growing polymer from the interface. The addition of diethylene glycol dimethacrylate gave capsules at 17 mol % PEGMA with ATRP, whereas conventional free-radical polymerization required 24 mol % PEGMA to form capsules. The lower PEGMA level required for capsule formation with ATRP was attributed to the lower rates of propagation and crosslinking and to improved incorporation of PEGMA into the final gels. Suspension ATRP with 24 mol % PEGMA in the feed gave two-layer capsule walls consisting of an inner layer visible by transmission electron microscopy and an outer layer visible by both transmission electron microscopy and environmental scanning electron microscopy, which indicated a compositional gradient across the capsule wall. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 156,171, 2006 [source] Synthesis and properties of crosslinked polyvinylformamide and polyvinylamine hydrogels in conjunction with silica particlesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2002Torsten Meyer Abstract Polyvinylamine hydrogels with silica particles encapsulated (PVAm/silica) were produced by a two-step synthesis. In the first step, polyvinylformamide/silica (PVFA/silica) hybrids were synthesized from vinylformamide (VFA) and 1,3-divinylimidazolidin-2-one (1,3-bisvinylethyleneurea, BVU), as the crosslinker, by radical copolymerization in silica/water suspensions using different compositions of VFA/BVU. The target product PVAm/silica was obtained by acidic hydrolysis of the PVFA/silica hydrogels in a second step. The chemical structures of both hydrogels, PVFA/silica and PVAm/silica, respectively, were revealed by solid-state 13C(1H) cross-polarity/magic-angle spinning NMR spectroscopy. Both hydrogels swelled significantly in water. The swelling capacity of the two systems was characterized by the correlation length , (or hydrodynamic blob size) of the network meshes with small-angle neutron scattering experiments. , is significantly larger for PVAm/silica than for PVFA/silica, which corresponds to the observed higher swelling capacity of this polyelectrolyte material. Furthermore, the swelling behavior of the hybrid hydrogels was quantitatively described in terms of free swell capacity, centrifuge-retention capacity, adsorption against pressure, and free swell rate as compared with values of the corresponding copolymer hydrogels. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3144,3152, 2002 [source] One-Pot Approach to Synthesize Star-Shaped Polystyrenes via RAFT-Mediated Radical CopolymerizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 22 2007Qingchun Liu Abstract Previously, we have reported a one-pot approach to generate star-shaped polymers by copolymerization of a maleimide inimer or bismaleimide hexane (BMIH) and a large excess of styrene (St) via atom transfer radical polymerization. Herein, we extended this approach towards the synthesis of star polystyrene through reversible addition fragmentation chain-transfer (RAFT)-mediated radical copolymerization of BMIH and an excess of St with cumyl dithiobenzoate (CDB) as a chain-transfer agent (CTA). It was illustrated that the PS arms were grafted from the preformed core, which was formed in situ during the copolymerization of BMIH and St. Therefore, this facile one-pot approach can be performed by applying different type of controlled radical polymerization. However, linear PS still was generated as a byproduct which had been observed previously. [source] Optically Active Methacrylic Copolymers Bearing Side-Chain Bisazoaromatic and Bulky Achiral MoietiesMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 14 2007Luigi Angiolini Abstract The synthesis of two novel series of optically active methacrylic copolymers that contain a side-chain chiral moiety linked to a photochromic bisazoaromatic chromophore has been carried out by radical copolymerization of the monomer (S)-3-methacryloyloxy-1-[4,-phenylazo-(4-azobenzene)]pyrrolidine with highly sterically hindered monomers such as tert- butyl methacrylate or triphenylmethyl methacrylate with the aim to investigate the effect on the optical activity of the resulting derivatives. The copolymeric products have been fully characterized and their spectroscopic and thermal properties compared to those of the related optically active homopolymer and the copolymers with methyl methacrylate, previously reported. The optical activity displayed by the polymers is discussed in terms of extent of chiral conformations assumed by the macromolecules as a consequence of the insertion of co-monomers capable of affecting the dipole-dipole interactions that occur in these derivatives between the side-chain bisazoaromatic chromophores disposed according to a mutual chiral arrangement. [source] N -Oxyl-Controlled Radical Copolymerization of Styrene with Ethyl , -CyanocinnamateMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 11 2004Andreas Bartsch Abstract Summary: The block copolymers of styrene and ethyl , -cyanocinnamate were prepared in dioxane and xylene with TEMPO-capped polystyrene (PSTEMPO) as macroinitiator. The copolymerizations were carried out at 125,°C and 135,°C. The reactivity ratios were determined according to Kelen Tüdos and compared with the reactivity ratios from the radical copolymerization of styrene and ethyl , -cyanocinnamate determined by Kohn et al. The influence of the comonomer ethyl , -cyanocinnamate on the glass transition temperature was studied in comparison with the corresponding homopolystyrene. Plots of conversion versus molecular weight distributions of the polymerizations with styrene at 125,°C. [source] Synthesis and Thermosensitive Properties of Poly[(N -vinylamide)- co -(vinyl acetate)]s and Their Hydrogels,MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2003Kazuya Yamamoto Abstract Free radical copolymerization of water-soluble N -vinylamides such as N -vinylacetamide (NVA) and N -vinylformamide (NVF) with hydrophobic vinyl acetate (VAc) gave amphiphilic copolymers. The monomer reactivity ratios were determined as r1,=,5.8 and r2,=,0.68 (M1,=,NVA, M2,=,VAc) and r1,=,6.2 and r2,=,0.37 (M1,=,NVF, M2,=,VAc), respectively. The growing radical of the terminals of N -vinylamides propagates more favorably for N -vinylamide monomers than for VAc monomer, resulting in the possible formation of blocky copolymers. It is found that aqueous solutions of these amphiphilic copolymers exhibited a lower critical solution temperature (LCST), depending on their chemical composition, followed by coacervate formation above the LCST. Furthermore, thermosensitive hydrogels could be prepared by the free radical copolymerization of N -vinylamide and VAc in the presence of the crosslinker butylenebis(N -vinylacetamide) (Bis-NVA). The swelling ratios of these hydrogels decreased with an immediate increase in temperature from 20 to 80,°C, and then reversibly increased with decreasing temperature. These hydrogels showed the same thermosensitive properties as linear copolymers of NVF and VAc. Relationship between LCST and vinyl acetate content in poly(N -vinylamide- co -VAc)s. [source] Acrylonitrile-Butadiene Rubber (NBR) Prepared via Living/Controlled Radical Polymerization (RAFT)MACROMOLECULAR RAPID COMMUNICATIONS, Issue 18 2010Andreas Kaiser Abstract In the current work we present results on the controlled/living radical copolymerization of acrylonitrile (AN) and 1,3-butadiene (BD) via reversible addition fragmentation chain transfer (RAFT) polymerization techniques. For the first time, a solution polymerization process for the synthesis of nitrile butadiene rubber (NBR) via the use of dithioacetate and trithiocarbonate RAFT agents is described. It is demonstrated that the number average molar mass, , of the NBR can be varied between a few thousand and 60,000,g,·,mol,1 with polydispersities between 1.2 and 2.0 (depending on the monomer to polymer conversion). Excellent agreement between the experimentally observed and the theoretically expected molar masses is found. Detailed information on the structure of the synthesized polymers is obtained by variable analytical techniques such as infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry, and electrospray ionization-mass spectrometry (ESI-MS). [source] Novel Photobleachable Deep UV Resists Based on Single Component Nonchemically Amplified Resist SystemMACROMOLECULAR RAPID COMMUNICATIONS, Issue 17 2005Jin-Baek Kim Abstract Summary: Photobleachable deep UV resists were designed by introducing diazoketo groups in polymer side chains. The diazoketo groups undergo the Wolff rearrangement upon irradiation in the deep UV, affording ketenes that react with water to provide base-soluble photoproducts. The polymers were synthesized by radical copolymerization of 2-(2-diazo-3-oxo-butyryloxy)-ethyl methacrylate, 2-hydroxyethyl methacrylate, and , -butyrolacton-2-yl methacrylate. The single component resist showed 0.7 µm line and space patterns using a mercury-xenon lamp in a contact printing mode. Scanning electron micrograph of 0.7 µm line and space patterns printed with polymer B at a dose of 70 mJ,·,cm,2. [source] | |||||||||||||