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Copolymer Composition (copolymer + composition)
Terms modified by Copolymer Composition Selected AbstractsCharacterization of New Amphiphilic Block Copolymers of N -Vinyl Pyrrolidone and Vinyl Acetate, 1 , Analysis of Copolymer Composition, End Groups, Molar Masses and Molar Mass Distributions,MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 8 2010Nick Fandrich Abstract New amphiphilic block copolymers consisting of N -vinyl pyrrolidone and vinyl acetate were synthesized via controlled radical polymerization using a reversible addition/fragmentation chain transfer (RAFT)/macromolecular design via the interchange of xanthates (MADIX) system. The synthesis was carried out in 1,4-dioxane as process solvent. In order to get conclusions on the mechanism of the polymerization the molecular structure of formed copolymers was analysed by means of different analytical techniques. 13C NMR spectroscopy was used for the determination of the monomer ratios. End groups were analysed by means of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This technique was also used to determine possible fragmentations of the RAFT end groups. By means of a combination of size exclusion chromatography, 13C NMR and static light scattering molar mass distributions and absolute molar masses could be analysed. The results clearly show a non-ideal RAFT mechanism. [source] Crystallization Behavior of Poly(, -caprolactone) Grafted onto Cellulose Alkyl Esters: Effects of Copolymer Composition and Intercomponent MiscibilityMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 20 2008Ryosuke Kusumi Abstract Graft copolymers of CA and CB with PCL were prepared at compositions rich in PCL. Kinetic DSC data were analyzed in terms of a folded-chain crystallization formula expanded for a binary mixing system of amorphous/crystalline polymers. The order of crystallization rates was plain PCL,>,CA- g -PCL (DS,=,2.98),>,CB- g -PCL (DS,=,2.1,2.95),>,CA- g -PCL (DS,=,2.1,2.5), and the fold-surface free energy of the PCL crystals obeyed the reverse order. POM revealed a generally tardy growth of spherulites for all the graft copolymers. The slower crystallization process may be ascribed primarily to the compulsory effect of anchoring PCL chains onto the semi-rigid cellulose backbone. Intercomponent miscibility of the CA/PCL and CB/PCL pairs was also taken into consideration. [source] Cellulose Acetate- graft -Poly(hydroxyalkanoate)s: Synthesis and Dependence of the Thermal Properties on Copolymer CompositionMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 14 2004Yoshikuni Teramoto Abstract Summary: Several different series of cellulose acetate- graft -poly(hydroxyalkanoate)s (CA- g -PHAs) were synthesized over a wide range of compositions by the graft copolymerization of lactic acid, L -lactide, (R,S)- , -butyrolactone, , -valerolactone and , -caprolactone onto the residual hydroxyl positions of CA, by virtue of a suitable catalyst, solvent and procedure for each individual case. To achieve a diversity of molecular architectures of the respective graft copolymer series, the degree of acetyl substitution (acetyl DS) of the CA starting material was also varied, resulting in different levels of the intramolecular density of grafts. The CA- g -PHAs thus obtained were subjected to differential scanning calorimetric measurements and the relationship between their molecular structure and thermal transition behavior was estimated, in comparison with some semi-empirical equations available for polymer blends or comb-like polymers. In particular, the composition dependence of the Tgs of the graft copolymers was represented well in terms of a formula proposed by Reimschuessel for comb-like polymers, when CAs of acetyl DS ,2 were employed as a trunk polymer. The deviation of the glass transition data from the model function was discussed in connection with the manner of graft modification. [source] Toughening of Epoxy Resin by Methyl Methacrylate/2-Ethylhexyl Acrylate Copolymers: The Effect of Copolymer CompositionMACROMOLECULAR MATERIALS & ENGINEERING, Issue 12 2007Soraia Zaioncz Abstract MMA-EHA copolymers with different compositions and with a low amount of AA were synthesized and used as impact modifier for epoxy networks. The effect of the copolymers on the tensile and dynamic mechanical properties as well as impact resistance of the epoxy network was evaluated. The addition of 10 phr of low-molar-mass MMA-EHA copolymer with defined composition resulted in a significant increase in impact resistance without any significant changes in the tensile strength, modulus, and glass transition temperature. The morphology of the modified epoxy network depends upon the copolymer composition. [source] Microstructure of glycidylmethacrylate/vinyl acetate copolymers by two-dimensional nuclear magnetic resonance spectroscopyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2001A. S. Brar Abstract Glycidylmethacrylate/vinyl acetate copolymers were prepared by solution polymerization with benzene as a solvent and benzoyl peroxide as an initiator. Copolymer compositions were determined from 1H NMR spectra, and comonomer reactivity ratios were determined by the Kelen,Tudos (KT) method and the nonlinear least-squares error-in-variable method (EVM). The reactivity ratios obtained from KT and EVM were rG = 37.4 ± 12.0 and rV = 0.036 ± 0.019 and rG = 35.2 and rV = 0.03, respectively. Complete spectral assignments of 13C and 1H NMR spectra were done with the help of distortionless enhancement by polarization transfer and two-dimensional 13C,1H heteronuclear single quantum coherence and total correlation spectroscopy. The methyl, methine, and methylene carbon resonance showed both stereochemical and compositional sensitivity. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4051,4060, 2001 [source] Random Copolymer Films with Molecular-Scale Compositional Heterogeneities that Interfere with Protein AdsorptionADVANCED FUNCTIONAL MATERIALS, Issue 21 2009Salmaan H. Baxamusa Abstract Smooth surfaces with compositional heterogeneities at a molecular-length scale are presented with the goal of disrupting surface,protein interactions. These surfaces are synthesized by utilizing photoinitiated chemical vapor deposition (piCVD) to deposit thin films of random copolymers consisting of highly hydrophilic and highly hydrophobic comonomers. Swellability, wettability, and surface roughness could be systematically controlled by tuning the copolymer composition. The surface composition was dynamic, and the surface reconstructed based on the hydration state of the film. Proteins adsorbed to the copolymer films less readily than to either of the respective homopolymers, indicating a synergistic effect resulting from the random copolymer presenting molecular-scale compositional heterogeneity. These results provide direct evidence that protein adsorption can be disrupted by such surfaces and a simple analytical model suggests that the heterogeneities occur over areas encompassing 4,5 repeat units of the polymer. The synthetic method used to create these films can be used to coat arbitrary geometries, enabling practical utility in a number of applications. [source] Cover Picture: Multipotent Polymer Coatings Based on Chemical Vapor Deposition Copolymerization (Adv. Mater.ADVANCED MATERIALS, Issue 12 200612/2006) Abstract The cover shows that chemical vapor deposition can be used to prepare copolymer thin films, on varying substrates, that can bind two different ligands with high selectivity. In work reported by Lahann and co-workers on p.,1521, the actual ligand ratios on the surface can be controlled by varying the copolymer composition. This technology may find applications in biomedical devices, high-throughput screening platforms, microfluidic analysis devices, and diagnostic platforms. [source] Preparation and in vitro release of D,L -tetrahydropalmatine-loaded graft copolymer nanoparticlesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Yinglei Zhai Abstract D,L -tetrahydropalmatine (THP)-loaded poly{[,-maleic anhydride-,-methoxy-poly(ethylene glycol)]- co -(ethy cyanoacrylate)} (PEGECA) amphiphilic graft copolymer nanoparticles (PEGECAT NPs) were prepared by the nanoprecipitation technique. The effects of solvent property, temperature, copolymer composition, and drug feeding on the drug-loaded amount and size of PEGECAT NPs were investigated. The morphological structure of PEGECAT NPs was characterized by transmission electron microscopy (TEM), proton nuclear magnetic resonance (1H NMR), and the size was measured by laser particle size analyzer (LPSA). In vitro release behaviors of drug from PEGECAT NPs were examined by high-pressure liquid chromatography (HPLC). The results demonstrate that PEGECAT NPs take on a spherical morphology with an inner core and outer shell before and after in vitro release. THP can be incorporated into the hydrophobic core of PEGECAT NPs and the drug-loaded amount is higher than 5%. The release of THP from PEGECAT NPs is initially fast and then slows down. The accumulated release is lower than 40% after 48 h. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Comparative study of the hydrolytic degradation of glycolide/L -lactide/,-caprolactone terpolymers initiated by zirconium(IV) acetylacetonate or stannous octoateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Janusz Kasperczyk Abstract A series of copolymers have been synthesized by the ring-opening polymerization of glycolide, L -lactide, and ,-caprolactone with zirconium(IV) acetylacetonate [Zr(Acac)4] or stannous octoate [Sn(Oct)2] as the catalyst. The resulting terpolymers have been characterized by analytical techniques such as proton nuclear magnetic resonance, size exclusion chromatography, and differential scanning calorimetry. Data have confirmed that Sn(Oct)2 leads to less transesterification of polymer chains than Zr(Acac)4 under similar conditions. The various copolymers have been compression-molded and allowed to degrade in a pH 7.4 phosphate buffer at 37°C. The results show that the degradation rate depends not only on the copolymer composition but also on the chain microstructure, the Sn(Oct)2 -initiated copolymers degrading less rapidly than Zr(Acac)4 -initiated ones with more random chain structures. The caproyl component appears the most resistant to degradation as its content increases in almost all cases. Moreover, caproyl units exhibit a protecting effect on neighboring lactyl or glycolyl units. The glycolyl content exhibits different features: it decreases because of faster degradation of glycolyl units, which are more hydrophilic than caproyl and lactyl ones, remains stable in the case of abundant CGC sequences, which are very resistant to degradation, or even increases because of the formation of polyglycolide crystallites. Terpolymers can crystallize during degradation if the block length of one of the components is sufficiently long, even though they are amorphous initially. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Online estimation and control of polymer quality in a copolymerization reactorAICHE JOURNAL, Issue 5 2002Myung-June Park The validity of an online state estimator for a semi-batch MMA/MA solution copolymerization reactor was established using online densitometer and viscometer. Using the conventional extended Kalman filter (EKF) as the state estimator, the experiment was conducted under both isothermal and nonisothermal conditions for application to the control of copolymer properties. Further analysis was made by using ofline measurement data for the mol fraction of MMA in the remaining monomers and the solid content. The EKF was found to provide a good estimate for the state of the copolymerization system. A model predictive controller was designed and implemented to obtain copolymers with uniform copolymer composition and the desired weight average molecular weight by adopting the feed flow rate of MMA and the reaction temperature as control inputs. The controller was proven effective with a satisfactory performance for the control of polymer properties in the semi-batch copolymerization reactor. [source] Synthesis and characterization of thermoresponsive polymers containing reduction-sensitive disulfide linkageJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2009Lihua Li Abstract A novel class of thermoresponsive and reduction-sensitive polymer, p(PEG-MEMA- co -Boc-Cyst-MMAm), containing disulfide linkages and removable hydrophobic tert -butyloxycarbonyl side chains was synthesized. The cloud points (CP) of p(PEG-MEMA- co -Boc-Cyst-MMAm) in water determined by UV/VIS spectrometer were between 20 °C and 57 °C, which shows that the CP can be tuned by adjusting the copolymer composition. Moreover, the thermosensitive polymers p(PEG-MEMA- co -Boc-Cyst-MMAm) formed stable nanoparticles in neutral aqueous medium, but rapidly destabilized in an reductive environment mimicking the intracellular space making them suitable for cytoplasmic drug delivery. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5989,5997, 2009 [source] Solid acid clay mediated copolymerization of methyl acrylate and 1-octene: 2D NMR substantiation of predominant alternating comonomer sequenceJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2009Sukhdeep Kaur Abstract Montmorillionite K10 powder presence during radically initiated copolymerization of methyl acrylate (M) and 1-octene (O) gave copolymers with higher incorporation of alkene unit. Highly viscous and transparent copolymers showed alternation irrespective of the copolymer composition. Increasing the amount of K10 powder increased the total percentage conversion, as well as 1-octene incorporation. The monomodal curves obtained in gel permeation chromatography (GPC) substantiated that true copolymers were formed. The alternation in the copolymers was authenticated through Heteronuclear Multiple Quantum Correlation (HMQC) experiments in conjugation with Total Correlated Spectroscopy (TOCSY). © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2156,2162, 2009 [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] Synthesis and characterization of sulfonated poly(benzoxazole ether ketone)s by direct copolymerization as novel polymers for proton-exchange membranesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2007Jinhuan Li Abstract A new series of sulfonated poly(benzoxazole ether ketone)s (SPAEKBO-X) were prepared by the aromatic nucleophilic polycondensation of 4,4,-(hexafluoroisopropylidene)-diphenol with 2,2,-bis[2-(4-fluorophenyl)benzoxazol-6-yl]hexafluoropropane and sodium 5,5,-carbonylbis-2-fluorobenzenesulfonate in various ratios. Fourier transform infrared and 1H NMR were used to characterize the structures and sulfonic acid contents of the copolymers. The copolymers were soluble in N -methyl-2-pyrrolidinone, N,N -dimethylacetamide, and N,N -dimethylformamide and could form tough and flexible membranes. The protonated membranes were thermally stable up to 320 °C in air. The water uptake, hydrolytic and oxidative stability, and mechanical properties were evaluated. At 30,90 °C and 95% relative humidity, the proton conductivities of the membranes increased with the sulfonic acid content and temperature and almost reached that of Nafion 112. At 90,130 °C, without external humidification, the conductivities increased with the temperature and benzoxazole content and reached above 10,2 S/cm. The SPAEKBO-X membranes, especially those with high benzoxazole compositions, possessed a large amount of strongly bound water (>50%). The experimental results indicate that SPAEKBO-X copolymers are promising for proton-exchange membranes in fuel cells, and their properties might be tailored by the adjustment of the copolymer composition for low temperatures and high humidity or for high temperatures and low humidity; they are especially promising for high-temperature applications. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2273,2286, 2007 [source] Binary copolymerization with full depropagation: A study of methyl methacrylate/,-methyl styrene copolymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2005M. J. Leamen Abstract The kinetics of the copolymerization of ,-methyl styrene and methyl methacrylate (MMA) have been revisited for the bulk system. Reactivity ratios and other kinetic parameter estimates based upon a copolymerization model developed by Kruger et al. (Makromol Chemie 1987, 188, 2163,2175) have been determined for a range of temperatures (60,140 °C). An interesting phenomenon has been uncovered, which shows that there is a distinct difference in copolymer composition predicted by the model when compared with experimental data at feed ratios of MMA below a critical value. This deviation also appears to be influenced by the reaction temperature. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3868,3877, 2005 [source] Copolymerization of (2-phenyl-1,3-dioxolane-4-yl)methyl methacrylate with alkyl methacrylates: Reactivity ratios and copolymer characterizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2002Mehmet Co Abstract The radical copolymerizations of (2-phenyl-1,3-dioxolane-4-yl-)methyl methacrylate (PDMMA) with methyl methacrylate (MMA), ethyl methacrylate (EMA), and butyl methacrylate (BMA) were studied in dioxane at 60 °C with benzoyl peroxide as an initiator. The glass-transition temperatures of poly(PDMMA- co -MMA), poly(PDMMA- co -EMA), and poly(PDMMA- co -BMA) varied from 130 to 138 °C, from 100 to 134 °C, and from 63 to 122 °C, respectively, depending on the copolymer composition. Along with some physicochemical properties and thermal stability investigations of the copolymers, the monomer reactivity ratios were also determined with the conventional Finemann,Ross and Kelen,Tüdös linearization methods. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1184,1191, 2002 [source] Solid polymer electrolytes III: Preparation, characterization, and ionic conductivity of new gelled polymer electrolytes based on segmented, perfluoropolyether-modified polyurethaneJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2002Chi-Chang Chen Abstract New segmented polyurethanes with perfluoropolyether (PFPE) and poly(ethylene oxide) blocks were synthesized from a fluorinated macrodiol mixed with poly(ethylene glycol) (PEG) in different ratios as a soft segment, 2,4-toluene diisocyanate as a hard segment, and ethylene glycol as a chain extender. Fourier transform infrared, NMR, and thermal analysis [differential scanning calorimetry and thermogravimetric analysis (TGA)] were used to characterize the structures of these copolymers. The copolymer films were immersed in a liquid electrolyte (1 M LiClO4/propylene carbonate) to form gel-type electrolytes. The ionic conductivities of these polymer electrolytes were investigated through changes in the copolymer composition and content of the liquid electrolyte. The relative molar ratio of PFPE and PEG in the copolymer played an important role in the conductivity and the capacity to retain the liquid electrolyte solution. The copolymer with a 50/50 PFPE/PEG ratio, having the lowest decomposition temperature shown by TGA, exhibited the highest ionic conductivity and lowest activation energy for ion transportation. The conductivities of these systems were about 10,3 S cm,1 at room temperature and 10,2 S cm,1 at 70 °C; the films immersed in the liquid electrolyte with an increase of 70 wt % were homogenous with good mechanical properties. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 486,495, 2002; DOI 10.1002/pola.10119 [source] Terpolymerization monitoring with ATR-FTIR spectroscopyJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2001Hong Hua Abstract Butyl acrylate, methyl methacrylate, and vinyl acetate solution and emulsion terpolymerizations were conducted. Attenuated total relflection-Fourier transform infrared spectroscopy equipped with conduit and diamond-composite sensor technology was used to monitor solution terpolymerizations off-line and emulsion terpolymerizations in-line. Monomer conversion and terpolymer composition changes as a function of time were calculated by monitoring the peak height of characteristic absorbances of each monomer. Results obtained from the ReactIRÔ 1000 reaction-analysis system agreed well with those determined by traditional gravimetry and 1H NMR spectroscopy. For the solution terpolymerizations, improved models developed previously to incorporate solvent effects on solution polymerizations of butyl acrylate and vinyl acetate monomers were applied to predict monomer conversion, copolymer composition, and molecular weight averages. Comparisons between experimental data and model predictions are presented. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1860,1876, 2001 [source] The Influence of Pendant Hydroxyl Groups on Enzymatic Degradation and Drug Delivery of Amphiphilic Poly[glycidol- block -(, -caprolactone)] CopolymersMACROMOLECULAR BIOSCIENCE, Issue 11 2009Jing Mao Abstract An amphiphilic diblock copolymer PG- b -PCL with well-controlled structure and pendant hydroxyl groups along hydrophilic block was synthesized by sequential anionic ring-opening polymerization. The micellization and drug release of PG- b -PCL copolymers using pyrene as a fluorescence probe were investigated for determining the influences of copolymer composition and lipase concentration on drug loading capacity and controlled release behavior. The biodegradation of PG- b -PCL copolymers was studied with microspheres as research samples. It has been concluded that the polar hydroxyl groups along each repeat unit of hydrophilic PG block in PG- b -PCL copolymer have great influences on drug encapsulation, drug release, and enzymatic degradation of micelles and microspheres. [source] Photocurable Shape-Memory Copolymers of , -Caprolactone and L -LactideMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 16 2010Minoru Nagata Abstract Biodegradable and photocurable block copolymers of , -caprolactone and L -lactide were synthesized by polycondensation of PLLA diol (,=,10,000,g,·,mol,1), PCL diol (,=,10,000,g,·,mol,1), and a chain extender bearing a coumarin group. The effect of copolymer composition on the thermal and mechanical properties of the photocured copolymers was studied by means of DSC and cyclic tensile tests. An increase in Young's modulus and a decrease in the tensile strain with increasing PLLA content was observed for the block copolymers. Block copolymers with high PCL content showed good to excellent shape-memory properties. Random copolymers exhibited Rf and Rr values above 90% at 45,°C for an extremely large tensile strain of 1,000%. [source] Toughening of Epoxy Resin by Methyl Methacrylate/2-Ethylhexyl Acrylate Copolymers: The Effect of Copolymer CompositionMACROMOLECULAR MATERIALS & ENGINEERING, Issue 12 2007Soraia Zaioncz Abstract MMA-EHA copolymers with different compositions and with a low amount of AA were synthesized and used as impact modifier for epoxy networks. The effect of the copolymers on the tensile and dynamic mechanical properties as well as impact resistance of the epoxy network was evaluated. The addition of 10 phr of low-molar-mass MMA-EHA copolymer with defined composition resulted in a significant increase in impact resistance without any significant changes in the tensile strength, modulus, and glass transition temperature. The morphology of the modified epoxy network depends upon the copolymer composition. [source] Microwave-Assisted Free Radical Copolymerizations of Styrene and Methyl MethacrylateMACROMOLECULAR RAPID COMMUNICATIONS, Issue 4 2007Heiner Stange Abstract Free radical copolymerizations of styrene and MMA were performed in toluene and DMF as solvents using different peroxide initiators with and without microwave irradiation. A general trend showed significant solvent dependence of monomer conversion rate only for copolymerizations initiated by tert -butyl perbenzoate in DMF compared to toluene but nearly no impact for copolymerizations initiated by dicumyl peroxide and dibenzoyl peroxide. Significant variations in copolymer composition were not observed for reactions under conventional heating compared to microwave irradiation. It was concluded that enhanced initiator decomposition under microwave irradiation in DMF accelerate polymerization of styrene and MMA by formation of larger amount of initiator radicals. [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] Feasible compositions for random copolymerizations,POLYMER ENGINEERING & SCIENCE, Issue 2 2001Raymond L. Smith Using the attainable region approach, feasible compositions and conversions for random copolymers are determined, along with altermatives for the related reactor configurations. This analysis attempts to find all of the possible compositions that can be produced by any system of reactros and mixing. The average copolymer compositions are bounded by the feed composition and the instantaneous copolymer composition produced at the initial conditions. Since the instantaneous copolymer composition can be found through the Mayo-Lewis equation, that case and the feed composition mark the limiting feasible compositions. The results can also be used to determine the range of feed compositions for which a specific copolymer product composition is possible. If the addition of monomer at any point in the reactor system is possible, e.g., by side-feeding, the analysis indicates that any desired copolymer composition can be obtained. [source] Hydrogen bond-mediated self-assembly and supramolecular structures of diblock copolymer mixturesPOLYMER INTERNATIONAL, Issue 5 2009Shiao-Wei Kuo Abstract This review summarizes recent advances in the preparation of hydrogen bonding block copolymer mixtures and the supramolecular structures they form through multiple hydrogen bonding interactions. Hydrogen bonding in block copolymer mixtures that form nanostructures and have unusual electronic, photonic and magnetic properties is a topic of great interest in polymer science. Combining the self-assembly of block copolymers with supramolecular structures offers unique possibilities to create new materials with tunable and responsive properties. The self-assembly of structures from diblock copolymer mixtures in the bulk state is readily controlled by varying the weight fraction of the block copolymer mixture and the copolymer composition; in solution, the morphologies are dependent on the copolymer composition, the copolymer concentration, the nature of the common solvent, the amount of the selective solvent and, most importantly, the hydrogen bonding strength. Copyright © 2008 Society of Chemical Industry [source] Preparation, characterization, and thermal properties of hydrophilic copolymers: p -chlorophenylmaleimides with hydroxylethyl methacrylate and ,-methyl itaconatePOLYMER INTERNATIONAL, Issue 9 2007Guadalupe del C Pizarro Abstract This work describes the synthesis, characterization, and thermal behavior of copolymers of p -chlorophenylmaleimide (Cl-PhMI) with ,-methyl itaconate (,-MHI) and 2-hydroxyethyl methacrylate (HEMA). Copolymerization was carried out with a radical initiator by varying the feed mole fraction of Cl-PhMI from 0.25 to 0.75. The copolymer composition was determined from the N/C ratio based on elemental analysis data and with 1H NMR spectroscopy for poly(Cl-PhMI- co -HEMA) using a proton signal attributed to the CH3 of HEMA (, = 0.7,1.4 ppm) and the area of aromatic ring protons (, = 7.2,7.8 ppm), where the proton/area relationship confirmed the copolymer compositions calculated by elemental analysis. The monomer reactivity ratios r1 and r2 were determined using the Kelen,Tüdös method. These values demonstrated that copolymerization produced random copolymers with an alternation tendency. The molecular weight and polydispersity were also determined. The thermal behavior can be correlated with the copolymer composition. An increase of the thermal decomposition temperature occurred when the content of Cl-PhMI increased. The glass transition temperature and thermal stability of poly(,-MHI) or poly(HEMA) increased with an increasing amount of Cl-PhMI in the polymer backbone. Copyright © 2007 Society of Chemical Industry [source] Water sorption into poly[(2-hydroxyethyl methacrylate)- co -(1-vinyl-2-pyrrolidone)]at 310 KPOLYMER INTERNATIONAL, Issue 11 2003Mark Malak Abstract Poly(2-hydroxyethyl methacrylate) and copolymers of 2-hydroxyethyl methacrylate (HEMA) and 1-vinyl-2-pyrrolidone (VP) in the form of cylindrical samples (,8 mm × 20 mm) have been prepared and the sorption of water into these cylinders has been studied by the mass-uptake methods and by magnetic-resonance imaging. The equilibrium water contents for the cylinders were found to vary systematically with the copolymer composition. Diffusion of water into the cylinders was found to follow Fickian behaviour for cylinders with high HEMA contents, with the diffusion coefficients obtained from mass-uptake studies dependent on the copolymer composition, varying from 1.7 × 10,11 m2 s,1 for poly(HEMA) to 2.0 × 10,11 m2 s,1 for poly(HEMA- co -VP) with a composition of 1:1. However, NMR-imaging studies showed that, while the profiles of the water diffusion fronts for cylinders with high HEMA contents were Fickian, that for the 1:1 copolymer was not and indicated that the mechanism was Case III. The polymers which were rich in VP were characterized by a water-sorption process which follows Case-III behaviour. Copyright © 2003 Society of Chemical Industry [source] Copolymerization of n -butylacrylate with methylmethacrylate by a novel photoinitiator, 1-(bromoacetyl)pyreneINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2007Anuradha Mishra The photopolymerization efficiency of pyrene (Py), 1-acetylpyrene (AP), and 1-(bromoacetyl)pyrene (BP) for copolymerization of n -butylacrylate (BA) with methylmethacrylate (MMA) was compared. A kinetic study of solution copolymerization in DMSO at 30 ± 0.2°C showed that the Py could not initiate copolymerization even after 20 h, whereas with AP as initiator, less than 1% conversion was observed. However, introduction of a Br in ,-methyl group of AP significantly enhanced the percent conversion. The kinetics and mechanism of copolymerization of BA with MMA using BP as photoinitiator have been studied in detail. The system follows nonideal kinetics (Rp,, [BP]0.67[BA]1[MMA]0.98), and degradative solvent transfer reasonably explains these kinetic nonidealities. The monomer reactivity ratios (MRRs) of MMA and BA have been estimated by the Finemann,Ross and Kelen,Tudos methods, by analyzing copolymer compositions determined by 1H-NMR spectra. The values of r1 (MMA) and r2 (BA) were found to be 2.17 and 0.44, respectively, which suggested the high concentration of alternating sequences in the random copolymers obtained. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 261,267, 2007 [source] | |||||||||||||||||||||||||