Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Terms modified by Comonomer

  • comonomer composition
  • comonomer concentration
  • comonomer content
  • comonomer incorporation

  • Selected Abstracts

    NMR Characterization of Carbazole-Substituted Norbornene Comonomer 9-(Bicyclo[2.2.1.]hept-5-en-2-ylmethyl)-9H -carbazole (BHMCZ) and Poly(ethylene- co -BHMCZ) Copolymer

    Ilpo Mustonen
    Abstract Carbazole-substituted norbornene comonomer 9-(bicyclo[2.2.1.]hept-5-en-2-ylmethyl)-9H -carbazole (BHMCZ) can be copolymerized with ethylene using the [Ph2C(Ind)(Cp)ZrCl2] catalyst and methylaluminoxane (MAO) cocatalyst system. The microstructures of BHMCZ comonomer and of ethylene,BHMCZ copolymer containing 4.6 mol-% BHMCZ units in the chain were characterized by one-dimensional 13C DEPT and two-dimensional homonuclear 1H- 1H COSY and heteronuclear 1H- 13C HXCO NMR spectroscopy. The BHMCZ comonomer appears as endo and exo stereoisomers, which were identified on the basis of chemical shifts, signal multiplicities, and coupling in the 2D NMR spectra. The NMR information on the BHMCZ isomers was used to assist in the determination of the chemical shifts and microstructure of ethylene,BHMCZ copolymer. The NMR analysis of ethylene,BHMCZ copolymer indicated that exo -BHMCZ polymerizes with ethylene slightly more readily than does endo -BHMCZ under the polymerization conditions employed. Isolated segments of exo(2)- exo(5)- exo(6) and endo(2)- exo(5)- exo(6) ethylene-BHMCZ copolymer showing carbon atom numbering. [source]

    Use of the Surfmer 11-(Methacryloyloxy) undecanylsulfate MET as a Comonomer in Polystyrene and Poly(methyl methacrylate)

    P.C. Hartmann
    Abstract The polymerizable surfactant sodium 11-(methacryloyloxy) undecanylsulfate (MET) has been synthesized with high purity, and its thermal stability and phase transitions have been studied by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively. MET has been copolymerized in solution with methylmethacrylate (MMA) or styrene (S), initiated by azo-bis-isobutyronitrile (AIBN). The copolymers thus obtained have been studied by Gel Permeation Chromatography (GPC), Transmission Electron Microscopy (TEM), and DSC. Due to the incompatibility between the polar head of the MET units and the non polar S or MMA units, MET units organize in the amorphous polymer matrix and arrange in lamellar structures. [source]

    Dye-Doped Polyhedral Oligomeric Silsesquioxane (POSS)-Modified Polymeric Matrices for Highly Efficient and Photostable Solid-State Lasers

    Roberto Sastre
    Abstract Here, the design, synthesis, and characterization of laser nanomaterials based on dye-doped methyl methacrylate (MMA) crosslinked with octa(propyl-methacrylate) polyhedral oligomeric silsesquioxane (8MMAPOSS) is reported in relation to their composition and structure. The influence of the silicon content on the laser action of the dye pyrromethene 567 (PM567) is analyzed in a systematic way by increasing the weight proportion of POSS from 1 to 50%. The influence of the inorganic network structure is studied by replacing the 8MMAPOSS comonomer by both the monofunctionalized heptaisobutyl-methacryl-POSS (1MMAPOSS), which defines the nanostructured linear network with the POSS cages appearing as pendant groups of the polymeric chains, and also by a new 8-hydrogenated POSS incorporated as additive to the polymeric matrices. The new materials exhibit enhanced thermal, optical, and mechanical properties with respect to the pure organic polymers. The organization of the molecular units in these nanomaterials is studied through a structural analysis by solid-state NMR. The domain size of the dispersed phase assures a homogeneous distribution of POSS into the polymer, thus, a continuous phase corresponding to the organic matrix incorporates these nanometer-sized POSS crosslinkers at a molecular level, in agreement with the transparency of the samples. The silicon,oxygen core framework has to be covalently bonded into the polymer backbone instead of being a simple additive and both the silica content and crosslinked degree exhibit a critical influence on the laser action. [source]

    Reactive grafting of glycidyl methacrylate onto polypropylene

    Emma-Louise Burton
    Abstract This work explored the melt-phase grafting of glycidyl methacrylate (GMA) onto polypropylene on a closely intermeshing corotating twin-screw extruder (16-mm screws, 40 : 1 length/diameter ratio). The modification of the base polypropylene to produce GMA-grafted polypropylene was achieved via peroxide-induced hydrogen abstraction from the polypropylene followed by the grafting of the GMA monomer or by the grafting of styrene followed by copolymerization with the GMA. In this study, both the position and order of the reactant addition were investigated as a route to improving graft yields and reducing side reactions (degradation). For the peroxide,GMA system, adding GMA to the melt before the peroxide resulted in significant improvements in the graft levels because of the improved dispersion of GMA in the melt. The addition of a comonomer (styrene) was explored as a second route to improving the graft yield. Although the addition of the comonomer led to a considerable rise in the level of grafted GMA, altering the order of the reactant addition was not found to contribute to an increase in the grafted GMA levels. However, variable levels of grafted styrene were achieved, and this may play an important role in the development of grafted polymers to suit specific needs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Ethylene/,-olefin copolymerization using diphenylcyclopentadienyl-phenoxytitanium dichloride/Al(iBu)3/[Ph3C][B(C6F5)4] catalyst systems

    Hongchun Li
    Abstract Copolymerization of ethylene with 1-octene and 1-octadecene using constrained geometry catalysts 2-(3,4-diphenylcyclopentadienyl)-4,6-di- tert -butylphenoxytitanium dichloride (1), 2-(3,4-diphenylcyclopentadienyl)-6- tert -butylphenoxytitanium dichloride (2), 2-(3,4-diphenylcyclopentadienyl)-6-methylphenoxytitanium dichloride (3), and 2-(3,4-diphenylcyclopentadienyl)-6-phenylphenoxytitanium dichloride (4) was studied in the presence of Al(iBu)3 and [Ph3C][B(C6F5)4](TIBA/B). The effect of the catalyst structure, comonomer, and reaction conditions on the catalytic activity, comonomer incorporation, and molecular weight of the produced copolymers was also examined. The 1/TIBA/B catalyst system exhibits high catalytic activity and produces high molecular weight copolymers. The melting temperature and the degree of crystallinity of the copolymers show a decrease with the increase in the comonomer incorporation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Synthesis, characterization, and comparison of properties of novel fluorinated poly(imide siloxane) copolymers

    Anindita Ghosh
    Abstract Four new poly(imide siloxane) copolymers were prepared by a one-pot solution imidization method at a reaction temperature of 180°C in ortho -dichlorobenzene as a solvent. The polymers were made through the reaction of o -diphthaleic anhydride with four different diamines,4,4,-bis(p -aminophenoxy-3,3,-trifluoromethyl) terphenyl, 4,4,-bis(3,-trifluoromethyl- p -aminobiphenyl ether)biphenyl, 2,6-bis(3,-trifluoromethyl- p -aminobiphenyl ether)pyridine, and 2,5-bis(3,-trifluoromethyl- p -aminobiphenylether)thiopene,and aminopropyl-terminated poly dimethylsiloxane as a comonomer. The polymers were named 1a, 1b, 1c, and 1d, respectively. The synthesized polymers showed good solubility in different organic solvents. The resulting polymers were well characterized with gel permeation chromatography, IR, and NMR techniques. 1H-NMR indicated that the siloxane loading was about 36%, although 40 wt % was attempted. 29Si-NMR confirmed that the low siloxane incorporation was due to a disproportionation reaction of the siloxane chain that resulted in a lowering of the siloxane block length. The films of these polymers showed low water absorption of 0.02% and a low dielectric constant of 2.38 at 1 MHz. These polyimides showed good thermal stability with decomposition temperatures (5% weight loss) up to 460°C in nitrogen. Transparent, thin films of these poly(imide siloxane)s exhibited tensile strengths up to 30 MPa and elongations at break up to 103%, which depended on the structure of the repeating unit. The rheological properties showed ease of processability for these polymers with no change in the melt viscosity with the temperature. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Using anionic polymerizable surfactants in ultrasonically irradiated emulsion polymerization to prepare polymer nanoparticles

    Yuhui He
    Abstract An ionic polymerizable surfactant, sodium sulfopropyl-laurylmaleate (M12), was synthesized and used as an emulsifier, an initiator, and a comonomer in ultrasonically irradiated emulsion polymerization. FTIR spectra and gravimetric method results indicated that copolymers P(Styrene-M12) and P(Butylacrlate-M12) were prepared successfully by ultrasonically irradiated emulsion polymerization and the composition of M12 elevated with the increasing concentration of M12 added. TEM photographs of P(St-M12) showed that the nanoparticles with small diameters (20,45 nm) were prepared. With the increase of M12 concentration, the particle size became smaller and the size distribution became wider. The P(BA-M12) particles size was also small (<100 nm) but the size distribution was wide due to the high reactivity of BA. Because surfmer M12 was chemically bonded with the latex particles, the stability of the copolymer latex prepared by ultrasonically irradiated emulsion polymerization was much better than that of the homopolymer latex (PSt or PBA) prepared by the same way. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Evaluation of the crystallization kinetics and melting of polypropylene and metallocene-prepared polyethylene blends

    Mohammad Razavi-Nouri
    Abstract The kinetics of the isothermal crystallization of a polypropylene (PP) random copolymer containing 5 mol % ethylene, a metallocene linear low-density polyethylene (m -LLDPE) with 3.3 mol % hexene-1 as a comonomer, and three blends were studied with differential scanning calorimetry at temperatures sufficiently high to prevent any crystallization of m-LLDPE. The analysis was carried out with the Avrami equation. The overall crystallization rate and the equilibrium melting temperature of the PP copolymer decreased with increasing amounts of m-LLDPE in the blends. The former was attributed to the effect of m-LLDPE in reducing the number of primary nuclei, and the latter was attributed to a lowering of the fold surface energy due to the limited partial miscibility of the blend components. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 634,640, 2007 [source]

    Synthesis and characterization of synthetic polymer colloids colloidally stabilized by cationized starch oligomers

    Marianne Gaborieau
    Abstract A method is developed for anchoring enzymatically degraded cationized starch as electrosteric stabilizers onto synthetic latices, using cerium(IV) to create free-radical grafting sites on the starch. Direct anchoring of debranched starch onto a poly(methyl methacrylate) seed latex yields a latex stabilized by well-defined oligosaccharides. Using ,-amylase to randomly cleave starch to form (1,4)-,-glucans, and a comonomer, N -isopropyl acrylamide (NIPAM), whose corresponding polymer exhibits a lower critical solution temperature (LCST), creates a means to synthesize block (or graft) oligomers of oligosaccharide and synthetic polymer, which are water soluble at room temperature. Above 30 °C, they become amphiphilic and form self-emulsifying nanoparticles (sometimes termed "frozen micelles") from which a synthetic latex is grown after addition of methyl methacrylate, the collapsed NIPAM-containing entities functioning as a type of in situ seed. This synthesis of stable synthetic latex particles is shown to have a high grafting efficiency. The starch fragments were characterized by 1H solution-state NMR before grafting, and 13C solid-state cross-polarization magic-angle spinning (CP-MAS) NMR was used to characterize the starch oligomers actually grafted on the final latex. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1836,1852, 2009 [source]

    Dispersion polymerization of vinyl monomers in supercritical carbon dioxide in the presence of drug molecules: A one-pot route for the preparation of controlled delivery systems

    Alessandro Galia
    Abstract The polymerization of 1-vinyl-2-pyrrolidone in supercritical carbon dioxide in the presence of ibuprofen as a model drug was investigated as a new one-pot process for the preparation of polymer-based drug delivery systems (DDSs). The composites were prepared at 65 °C and P = 31,42 MPa by changing the initial concentration of the drug and the concentration of a crosslinking agent and that of a hydrophobic comonomer. The effects of these parameters on the performances of the polymerization and on the in vitro release kinetics of ibuprofen were studied. In all the experiments, part of the drug was entrapped inside the polymer particles and dissolved more slowly with respect to the pure compound. Copolymerization with methyl methacrylate was the most effective route to obtain a DDS with sustained temporal release of the drug molecule. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7429,7446, 2008 [source]

    Amphiphilic gradient copolymers containing fluorinated 2-phenyl-2-oxazolines: Microwave-assisted one-pot synthesis and self-assembly in water

    Matthias Lobert
    Abstract Here, we present the one-step synthesis of 2-(m -difluorophenyl)-2-oxazoline and its use as a monomer for microwave-assisted statistical cationic ring-opening copolymerizations (CROP). Well-defined amphiphilic gradient copolymers, as evidenced by the polymerization kinetics, were prepared using 2-ethyl-2-oxazoline as comonomer and methyl tosylate as initiator in nitromethane at 140 °C. The resulting gradient copolymers (DP = 60 and 100) were characterized by means of size exclusion chromatography and 1H NMR spectroscopy. In the second part, we focus on a detailed study of the self-assembly of the copolymers in aqueous solution using atomic force microscopy and dynamic light scattering. Both methods revealed the self-assembly of the gradient copolymers into spherical micelles. To quantify the influence of the fluorine atoms and the monomer distribution on the self-assembly, a comparative study with gradient copolymers of 2-phenyl-2-oxazoline and 2-ethyl-2-oxazoline was performed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5859,5868, 2008 [source]

    High molar mass ethene/1-olefin copolymers synthesized with acenaphthyl substituted metallocene catalysts

    Erkki Aitola
    Abstract The influence of ligand structure on copolymerization properties of metallocene catalysts was elucidated with three C1 -symmetric methylalumoxane (MAO) activated zirconocene dichlorides, ethylene(1-(7, 9)-diphenylcyclopenta-[a]-acenaphthadienyl-2-phenyl-2-cyclopentadienyl)ZrCl2 (1), ethylene(1-(7, 9)-diphenylcyclopenta-[a]-acenaphthadienyl-2-phenyl-2-fluorenyl)ZrCl2 (2), and ethylene(1-(9)-fluorenyl-(R)1-phenyl-2-(1-indenyl)ZrCl2 (3). Polyethenes produced with 1/MAO had considerable, ca. 10% amount of trans -vinylene end groups, resulting from the chain end isomerization prior to the chain termination. When ethene was copolymerized with 1-hexene or 1-hexadecene using 1/MAO, molar mass of the copolymers varied from high to moderate (531,116 kg/mol) depending on the comonomer feed. At 50% comonomer feed, ethene/1-olefin copolymers with high hexene or hexadecene content (around 10%) were achievable. In the series of catalysts, polyethenes with highest molar mass, up to 985 kg/mol, were obtained with sterically most crowded 2/MAO, but the catalyst was only moderately active to copolymerize higher olefins. Catalyst 3/MAO produced polyethenes with extremely small amounts of trans -vinylene end groups and relatively low molar mass 1-hexene copolymers (from 157 to 38 kg/mol) with similar comonomer content as 1. These results indicate that the catalyst structure, which favors chain end isomerization, is also capable to produce high molar mass 1-olefin copolymers with high comonomer content. In addition, an exceptionally strong synergetic effect of the comonomer on the polymerization activity was observed with catalyst 3/MAO. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 373,382, 2008 [source]

    Selective polymerization of functional monomers with Novozym 435

    Martijn A. J. Veld
    Abstract Two novel monomers, ambrettolide epoxide and isopropyl aleuriteate, encompassing functional groups, were obtained in a single step from commercially available materials. Novozym 435 catalyzed ring opening polymerization of ambrettolide epoxide furnished a polymer of Mn = 9.7 kg/mol and PDI = 1.9 while the epoxide groups remained unaffected during the polymerization. Selective polymerization of the primary hydroxyl groups of isopropyl aleuriteate using Novozym 435 was feasible and a polymer with moderate molecular weight (Mn = 5.6 kg/mol, PDI = 3.2) was isolated in moderate yield (43%). Subsequently, copolymerization of isopropyl aleuriteate with ,-CL in different ratios was performed, resulting in soluble, hydroxy functional polymers with good molecular weights (Mn = 10.4,27.2 kg/mol) in good yield (71,78%). The secondary hydroxy groups in the polymer reacted easily with hexyl isocyanate, showing the potential of isopropyl aleuriteate as a comonomer for the synthesis of functional polyesters. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5968,5978, 2007 [source]

    Copolymerization of vinylcyclohexane with ethene and propene using zirconocene catalysts

    Erkki Aitola
    Abstract Vinylcyclohexane (VCH) was copolymerized with ethene and propene using methylaluminoxane-activated metallocene catalysts. The catalyst precursor for the ethene copolymerization was rac -ethylenebis(indenyl)ZrCl2 (1). Propene copolymerizations were further studied with Cs -symmetric isopropylidene(cyclopentadienyl)(fluorenyl)ZrCl2 (2), C1 -symmetric ethylene(1-indenyl-2-phenyl-2-fluorenyl)ZrCl2 (3), and "meso"-dimethylsilyl[3-benzylindenyl)(2-methylbenz[e]indenyl)]ZrCl2 (4). Catalyst 1 produced a random ethene,VCH copolymer with very high activity and moderate VCH incorporation. The highest comonomer content in the copolymer was 3.5 mol %. Catalysts 1 and 4 produced poly(propene- co -vinylcyclohexane) with moderate to good activities [up to 4900 and 15,400 kg of polymer/(mol of catalyst × h) for 1 and 4, respectively] under similar reaction conditions but with fairly low comonomer contents (up to 1.0 and 2.0% for 1 and 4, respectively). Catalysts 2 and 3, both bearing a fluorenyl moiety, gave propene,VCH copolymers with only negligible amounts of the comonomer. The homopolymerization of VCH was performed with 1 as a reference, and low-molar-mass isotactic polyvinylcyclohexane with a low activity was obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6569,6574, 2006 [source]

    Synthesis of an alkali-swellable emulsion and its effect on the rate of polymer diffusion in poly(vinyl acetate-butyl acrylate) latex films

    Jung Kwon Oh
    Abstract We describe the synthesis and characterization of a weakly cross-linked poly(methacrylic acid- co -ethyl acrylate) alkali-swellable emulsion (ASE), as well as an investigation of its influence on the rate of polymer diffusion in latex films. The films examined were formed from poly(vinyl acetate- co -butyl acrylate) latex particles containing a small amount of acrylic acid as a comonomer. Polymer diffusion rates were monitored by the energy transfer technique. We found that the presence of the ASE component, either in the acid form or fully neutralized by ammonia or sodium hydroxide, had very little effect on the polymer diffusion rate. However, in the presence of 2 wt % NH4 -ASE, there was a small but significant increase in the polymer diffusion rate. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5632,5642, 2005 [source]

    Nanoencapsulation of a hydrophobic compound by a miniemulsion polymerization process

    Yingwu Luo
    Abstract The nanoencapsulation of hydrophobic compounds by miniemulsion polymerization, a convenient one-step encapsulation technique for nanocapsules, was investigated in terms of the thermodynamics and kinetics. The encapsulation was achieved by polymerization inducing phase separation within minidroplets dispersed in an aqueous phase. Thermodynamic factors (the level and type of surfactant, the level of the hydrophilic comonomer, and the monomer/paraffin ratio), kinetic factors (the level of the crosslinking agent or chain-transfer agent), and nucleation modes were all found to have a great influence on the latex morphology. Specifically, for a styrene/paraffin system, there were optimum levels of sodium dodecyl sulfate (1.0 wt %), the hydrophilic comonomer (1.0 wt % methyl acrylate acid), and the chain-transfer agent (0.2 wt % n -dodecanethiol) for obtaining well-defined nanocapsules of paraffin with a styrene/paraffin ratio of 1:1. When the styrene/paraffin ratio was reduced, however, it was more difficult to achieve a fully encapsulated particle morphology. Homogeneous nucleation could compete with encapsulation, and this resulted in a pure polymer particle and a half-moon morphology. Conditions were also found under which complete encapsulation could be observed with a water-soluble initiator (potassium persulfate), contrary to certain reports. Replacing potassium persulfate with an oil-soluble initiator (2,2-azobisisobutyronitrile) had little influence on the morphology under those conditions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2145,2154, 2004 [source]

    Method of preparing clean poly(4-methylstyrene)- block -polyisobutene by the combination of sequential monomer addition and sequential initiation in the solvent CH3Cl

    Yuhong Ma
    A novel method of synthesizing a clean diblock copolymer via cationic polymerization was developed. First, a poly(4-methylstyrene) macroinitiator was prepared, and then a second comonomer (isobutene) and a coinitiator (AlEt2Cl) were added for the initiation of block copolymerization. [source]

    Influence of stereochemistry on the thermal properties of partially cycloaliphatic polyamides

    Bert Vanhaecht
    Abstract The effects of the partial substitution of 1,4-disubstituted cyclohexane monomers for linear aliphatic monomers in polyamides are discussed. More specifically, the relation between the stereochemistry of the cycloaliphatic residues and the thermal properties [melting temperature (Tm) and crystallization temperature (Tcr)] was investigated. For this purpose, two different types of copolyamides were synthesized: in polyamides 12.6, the adipic acid residues were partially replaced by cis/trans -1,4-cyclohexanedicarboxylic acid (1,4-CHDA), whereas in polyamides 4.14, the 1,4-diaminobutane residues were partially substituted with cis/trans -1,4-diaminocyclohexane (1,4-DACH). For both systems, increasing the degree of substitution of cycloaliphatic residues for linear aliphatic residues resulted in a rise of both Tm and Tcr. This points to the isomorphous crystallization of the linear and cycloaliphatic residues. In contrast to the use of 1,4-DACH as a comonomer, 1,4-CHDA residues showed isomerization upon thermal treatment of the polyamides. This isomerization of the cyclohexane residues influenced the thermal properties of the copolyamides. The use of a nonisomerizing cis,trans mixture of 1,4-DACH exhibited the large influence of the stereochemistry of the cycloaliphatic residues on the Tm of the copolyamides. For both the 1,4-CHDA- and 1,4-DACH-based copolyamides, differential scanning calorimetry analysis revealed that recrystallization occurs during melting. This exothermal effect becomes less pronounced with an increasing content of rigid cycloaliphatic residues. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1962,1971, 2002 [source]

    Copolymerization of propylene with various higher ,-olefins using silica-supported rac -Me2Si(Ind)2ZrCl2

    Jun-Ting Xu
    Abstract The copolymerization of propylene with 1-hexene, 1-octene, 1-decene, and 1-dodecene was carried out with silica-supported rac -Me2Si(Ind)2ZrCl2 as a catalyst. The copolymerization activities of the homogeneous and supported catalysts and the microstructures of the resulting copolymers were compared. The activity of the supported catalyst was only one-half to one-eighth of that of the homogeneous catalyst, depending on the comonomer type. The supported catalyst copolymerized more comonomer into the polymer chain than the homogeneous catalyst at the same monomer feed ratio. Data of reactivity ratios showed that the depression in the activity of propylene instead of an enhancement in the activity of olefinic comonomer was responsible for this phenomenon. We also found that copolymerization with ,-olefins and supporting the metallocene on a carrier improved the stereoregularity and regioregularity of the copolymers. The melting temperature of all the copolymers decreased linearly with growing comonomer content, regardless of the comonomer type and catalyst system. Low mobility of the propagation chain in the supported catalyst was suggested as the reason for the different polymerization behaviors of the supported catalyst with the homogeneous system. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3294,3303, 2001 [source]

    Molecular structure determination of Ni(II) diimine complex and DMA analysis of Ni(II) diimine-based polyethenes ,

    J. O. Liimatta
    Abstract Dynamic mechanical thermoanalysis showed that polyethene, prepared under suitable polymerization conditions with the Brookhart-type catalyst dibromo- N,N,-1,2-acenaphthylenediylidenebis[2,6-bis(1-methylethyl)benzeneamine]Ni(II)/methylaluminoxane (MAO), behaved like an elastomer, even though no comonomer was added. A structural characterization showed that the polymers contained methyl to hexyl branches and some longer branches. The effect of the polymerization conditions on branching was investigated through variations in the pressure and temperature of the polymerization. Depending on the degree and type of branching, polyethene was either quite amorphous or highly crystalline with a high melting temperature. The solid-state structure of the catalyst dibromo- N,N,-1,2-acenaphthylenediylidenebis[2,6-bis(1-methylethyl)benzeneamine]Ni(II) consisted of two centrosymmetrically related monomeric moieties, where Ni atoms were bridged by two bromide ligands. The Ni atom was five-coordinated, with a square pyramidal coordination polyhedron. The sixth coordination site of the octahedral geometry was effectively blocked by the isopropyl groups of the 2,6-C6H3(i -Pr) substituents of the diimine ligand. In solution in the presence of MAO, the longer bridging NiBr bonds broke, and the complex dissociated to a monomeric species. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1426,1434, 2001 [source]

    Synthesis and Characterization of , -Cyclodextrin Based Functional Monomers and its Copolymers with N -isopropylacrylamide

    Yu-Yang Liu
    Abstract Two novel monovinyl , -cyclodextrin (, -CD) monomers are synthesized. Their chemical compositions are characterized by means of element analysis, NMR and FT-IR spectroscopy. The results show that the synthesis techniques used are convenient and efficient. Using N -isopropylacrylamide as a comonomer, two novel linear copolymers can also be synthesized. Synthesis route of monovinyl , -CD monomers. [source]

    NMR Characterization of Carbazole-Substituted Norbornene Comonomer 9-(Bicyclo[2.2.1.]hept-5-en-2-ylmethyl)-9H -carbazole (BHMCZ) and Poly(ethylene- co -BHMCZ) Copolymer

    Ilpo Mustonen
    Abstract Carbazole-substituted norbornene comonomer 9-(bicyclo[2.2.1.]hept-5-en-2-ylmethyl)-9H -carbazole (BHMCZ) can be copolymerized with ethylene using the [Ph2C(Ind)(Cp)ZrCl2] catalyst and methylaluminoxane (MAO) cocatalyst system. The microstructures of BHMCZ comonomer and of ethylene,BHMCZ copolymer containing 4.6 mol-% BHMCZ units in the chain were characterized by one-dimensional 13C DEPT and two-dimensional homonuclear 1H- 1H COSY and heteronuclear 1H- 13C HXCO NMR spectroscopy. The BHMCZ comonomer appears as endo and exo stereoisomers, which were identified on the basis of chemical shifts, signal multiplicities, and coupling in the 2D NMR spectra. The NMR information on the BHMCZ isomers was used to assist in the determination of the chemical shifts and microstructure of ethylene,BHMCZ copolymer. The NMR analysis of ethylene,BHMCZ copolymer indicated that exo -BHMCZ polymerizes with ethylene slightly more readily than does endo -BHMCZ under the polymerization conditions employed. Isolated segments of exo(2)- exo(5)- exo(6) and endo(2)- exo(5)- exo(6) ethylene-BHMCZ copolymer showing carbon atom numbering. [source]

    Use of Hydroxyl Functionalized (Meth)acrylic Cross-Linked Polymer Microparticles as Chain Transfer Agent in Cationic Photopolymerization of Cycloaliphatic Epoxy Monomer, 1

    Ludovic Valette
    Abstract In the case of cationic-type photopolymerized epoxy networks, a new type of chain transfer agent based on hydroxyl functional acrylic cross-linked polymer microparticles (CPM, also called microgels) has been tested. The CPM functionality was obtained through hydroxyethyl acrylate (HEA) monomer, used as comonomer with butyl acrylate (BA) and hexane diol diacrylate (HDDA). Stabilizing monomers were also required for the synthesis of CPM. In order to compare their particular effects, 4 sets of CPM were synthesized with 4 different stabilizing agents, either hydroxyl functional or not. Consequently, two types of OH groups were present in the particles: primary groups coming from HEA and preferentially located in the particles, and optional hydroxyl groups due to the hydroxyl functional stabilizing agents which were mainly placed onto the particles' surface. The viscoelastic properties of the photopolymerized films have been used to obtain information about the chain transfer reaction and the network microstructure. In all cases, the rubber modulus, was improved because of the decrease of the number of dangling epoxy chains in the epoxy network. When hydroxyl groups were only present in the particles, the mobility of the linkages was assumed to be low, and the mechanical relaxation temperature, T,, strongly increased. However, CPM aggregation occurred at high CPM concentrations, lowering and T,. On the contrary, when OH groups were located both on the surface as well as inside the particles, no large CPM aggregation took place, even with [CPM],=,40 wt.-%. Nevertheless, the presumably higher mobility of the linkages on the particles' surface prevented any T, increase. The water absorption of all systems based on CPM was very low, around 2% whatever the concentration of chain transfer agent. Schematic description of the transfer reaction between a propagating cationic-type epoxy chain and a hydroxyl functional CPM. [source]

    Automated Raman Spectroscopy as a Tool for the High-Throughput Characterization of Molecular Structure and Mechanical Properties of Polyethylenes

    Claus Gabriel
    Abstract Raman spectroscopy, which does not require a time-consuming sample preparation, is described as an analytical tool for the high-throughput characterization of polyethylenes. The content of comonomer and the amount of methyl groups per 1,000 carbon atoms of polyethylenes can be predicted from Raman spectra using multivariate data analysis. In addition, macroscopic properties, such as density and elastic modulus as well as yield stress, can be derived from Raman spectra. Raman spectra of selected metallocene-catalyzed polyethylenes of different comonomer content. [source]

    Metallocene-Catalyzed Gas-Phase Ethylene Copolymerization: Kinetics and Polymer Properties

    Michiel F. Bergstra
    Abstract The influence of 1-hexene is examined on the kinetics of ethylene copolymerization with a metallocene catalyst in gas phase. A model is derived, which is able to describe a large reaction rate increase due to a small amount of incorporated comonomer. This complexation model describes the measured reaction rates for ethylene and 1-hexene, and the co-monomer incorporation. Polymer properties were analyzed, such as comonomer weight fraction. The density, melting point, and molecular weight of the produced polymer decreased with increase in 1-hexene gas concentration. The in situ 1-hexene sorption is estimated and follows Henry's law, but seems much higher than reported in the literature. [source]

    Multi-Component Kinetic Modeling for Controlling Local Compositions in Thermosensitive Polymers

    Todd Hoare
    Abstract Summary: An explicit terminal copolymerization kinetic model accounting for the copolymerization of up to four different comonomers is developed and applied to model the conversion profiles and local compositional gradients in functionalized PNIPAM-based polymer and hydrogel systems. The kinetics of the functional comonomer(s) have a large influence on both the mole fraction and chain distribution of functional groups in polymers. Strategies are developed to synthesize polymers with uniform compositions by applying semi-batch techniques or via copolymerization of multiple monomers with the same target functionality but with divergent reactivities relative to NIPAM. Synthetic protocols are also designed to maximize the compositional uniformity and randomness of ampholytic polymers. Instantaneous mole fractions of monomers in polymers as a function of the overall monomer conversion for the copolymerizations of NIPAM, MBA, and two functional monomers: MMA and acrylamide. [source]

    Reactive acrylic liquid rubber with terminal and pendant carboxyl groups as a modifier for epoxy resin

    D. Ratna
    Reactive acrylate rubbers with the terminal and pendent carboxyl groups have been investigated as a modifier for a room temperature curing epoxy resin. The liquid rubbers with varying molecular weights and carboxyl-functionality were synthesized by bulk polymerization of 2-ethyl hexyl acrylate using acrylic acid as a comonomer. The liquid rubbers were characterized by FTIR, 13C NMR spectroscopic analysis, nonaqueous titration, vapor pressure osmometry, and solubility characteristics. The liquid rubbers were incorporated into the epoxy resin by the prereact method and the effect of functionality on impact properties of the modified networks were investigated. The results were explained in terms of dynamic mechanical properties and morphology analyzed by scanning electron microscope (SEM). Polym. Eng. Sci. 47:26,33, 2007. © 2006 Society of Plastics Engineers. [source]

    Formation of a fibrillar morphology of crosslinked epoxy in a polystyrene continuous phase by reactive extrusion

    Françoise Fenouillot
    An immiscible polymer blend where the dispersed phase is fibrillar was prepared by in situ crosslinking of the minor phase. A model polystyrene/epoxy-amine blend was selected on the basis of rheological (achievement of the fibrillar structure) and reactivity (fast crosslinking) criteria. The system was a polystyrene/diglycidyl ether of bisphenol A (DGEBA)-aminoethyl piperazine (AEP) blend. At the temperature of extrusion, 180°C, the DGEBA is immiscible in PS and heterogeneous material is obtained. The elongational flow imposed by drawing the extrudate at the die exit permitted controlled generation of a fibrillar morphology of the dispersed epoxy phase, with a fiber diameter of 1 ,m and an aspect ratio greater than 100. It was shown that when the amine comonomer was injected into the extruder, its reactivity with DGEBA at high temperature was high enough to ensure partial crosslinking of the epoxy. The fibrils were formed even though the gel point of the epoxy phase was exceeded. However, above a certain critical insoluble fraction that we estimated to be between 45% and 70%, a coarsening of the structure appeared, caused by the decreasing deformability of the domains and their coalescence. Finally, for our system, the crosslinking of the dispersed phase up to 90% of insoluble fraction did not totally stabilize the morphology after the second processing step (injection molding). Polym. Eng. Sci. 44:625,637, 2004. © 2004 Society of Plastics Engineers. [source]

    Styrene/substituted styrene copolymerization by Ph2Zn,metallocene,MAO systems: homo- and copolymerization of p -methoxystyrene with styrene,

    Franco M Rabagliati
    Abstract BACKGROUND: The present work is part of a general study regarding the homo- and copolymerization of styrene using diphenylzinc,additive initiator systems, with the aim of improving the properties of commercial atactic polystyrene. The study is focused on syndiotactic polystyrene and/or copolymers of styrene (S) with substituted styrene, styrene derivatives or various ,-olefins. This research has been ongoing over the last 15 years. RESULTS: The reported experiments show that binary metallocene,methylaluminoxane (MAO) and ternary Ph2Zn,metallocene,MAO, depending on the metallocene employed, are capable of inducing both homo- and copolymerization of styrene and p -methoxystyrene (p -MeOS). The results indicate that for a styrene/p -MeOS mole ratio with p -MeOS > 25% the product obtained has only a minor incorporation of styrene units. The efficiency of the metallocenes studied follows the order bis(n -butylcyclopentadienyl)titanium dichloride ((n -BuCp)2TiCl2) > indenyltitanium trichloride (IndTiCl3) > Cp2TiCl2. CONCLUSION: Metallocenes (n -BuCp)2TiCl2, Cp2TiCl2 and IndTiCl3 in binary systems combined with MAO, as well as in ternary systems combined with Ph2Zn and MAO, induce the homopolymerization of p -MeOS and its copolymerization with styrene. The styrene/p -MeOS copolymer obtained was enriched in p -MeOS with respect to the initial feed, in agreement with the I+ inductive effect of the methoxy group in the para position of styrene. As already reported, the role of Ph2Zn was nullified by its complexation with the p -MeOS comonomer. Copyright © 2008 Society of Chemical Industry [source]

    Preparation and properties of silicone-containing poly(methyl methacrylate) gels

    Hamid Javaherian Naghash
    Abstract Poly(methyl methacrylate) (PMMA) gels with varying amounts of silicone and solvent and constant amounts of crosslinker were prepared by solution free radical crosslinking copolymerization of methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDM), tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) comonomer systems. They were then studied in benzene at a total monomer concentration of 3.5 mol L,1 and 70 °C. The conversion of monomer, volume swelling ratio, weight fraction and gel point were measured as a function of the reaction time, silicone concentration and benzene content up to the onset of macrogelation. Structural characteristics of the gels were examined by using equilibrium swelling in benzene, gel fraction and Fourier-transform infrared (FTIR) analysis. The morphology of the copolymers was also investigated by SEM. Based on the obtained results, it was concluded that the FTIR data did not have the capacity to show the presence of the VTES or TEOS moiety in these kinds of copolymers. On the other hand, the variation of weight fraction of gel, Wg, and its equilibrium volume swelling ratio in benzene, qv, exhibited the same behaviour as that of MMA/EGDM copolymers. Also, the dilution of the monomer mixture resulted in an increase in the gel point and swelling degree and a decrease in the percent of conversion and gel fraction. Finally, TEOS is not an ideal silicone compound for reaction in the MMA/EGDM copolymerization system, whereas VTES is a suitable silicone comonomer for this system and it has been proved useful. Copyright © 2005 Society of Chemical Industry [source]