Showing papers on "Methyl acrylate published in 2002"

Atom transfer radical polymerization from cellulose fibers at ambient temperature.

Abstract: Cellulose fibers have been successfully grafted with poly(methyl acrylate) using atom transfer radical polymerization, mediated by Me6-TREN and Cu(I)Br at ambient temperature The initially hydroph

Origin of Inhibition Effects in the Reversible Addition Fragmentation Chain Transfer (RAFT) Polymerization of Methyl Acrylate

Abstract: The reversible addition fragmentation chain transfer (RAFT) bulk polymerization of a fast propagating monomer (methyl acrylate, MA) has been studied using 1-phenylethyl dithiobenzoate (1-PEDB) and 2-(2-cyanopropyl) dithiobenzoate (CPDB) as RAFT agents at 60 °C. Rate retardation with increasing initial RAFT agent concentrations is common to both 1-PEDB- and CPDB-mediated MA polymerizations and occurs in comparable magnitude. A pronounced inhibition period is observed in 1-PEDB-mediated MA polymerizations, whereas the corresponding CPDB-mediated polymerizations show considerably less inhibition. The cause for this inhibition may either be associated with the leaving group of the initial RAFT agent or with the slow fragmentation of the initial intermediate macroRAFT radical. The present experimental data suggest that slow fragmentation is the probable cause for inhibition. We conclude that the radical intermediate formed by addition of radicals to the initial RAFT agent is different in stability than the macroRAFT radical formed analogously from macroRAFT agent. The inhibition period is effectively reduced by the use of CPDB as the initial RAFT agent in methyl acrylate polymerizations.

The leaching and re-deposition of metal species from and onto conventional supported palladium catalysts in the Heck reaction of iodobenzene and methyl acrylate in N-methylpyrrolidone

Abstract: When supported palladium catalysts are used for Heck vinylation of iodobenzene with methyl acrylate in N-methylpyrrolidone (NMP) in the presence of triethylamine and sodium carbonate bases, the reaction proceeds homogeneously with dissolved active palladium species that are formed through coordination of NMP and triethylamine with palladium. These active species easily react with iodobenzene (oxidative addition), beginning the catalytic cycle of Heck coupling. The last step of catalyst regeneration takes place with the action of sodium carbonate. The active palladium species are not stable and deposit the metal to support when they cannot find iodobenzene to react in the reaction mixture after this substrate is completely consumed. The re-deposition of palladium occurs on the surfaces of bare support and/or palladium particles remaining on it, depending on the nature of support surface and the number and size of residual metal particles. The growth of palladium particles has been observed after the reuse of catalyst in some case. However, the supported catalysts are recyclable without loss of activity.

Controlled copolymerization of methyl acrylate with olefins under mild conditions

Abstract: A copper-mediated process for the synthesis of random copolymers of methyl acrylate with non-polarolefins, ranging from ethene to 1-octene, norbornene and norbornene derivatives, and capable of synthesizing copolymers having greater than 5% incorporation of the olefin, as well as copolymers synthesized using the process are described. The process displays many of the characteristics of a living polymerization process: the polydispersities of the copolymers obtained are less than about 1.7, preferably from about 1.1 to about 1.4, and it is possible to synthesize novel block terpolymers of methyl acrylate with olefins by the sequential addition of the latter monomers.

Synthesis, Characterization, and Properties of ABA Type Triblock Copolymer Brushes of Styrene and Methyl Acrylate Prepared by Atom Transfer Radical Polymerization

Abstract: A tethered triblock copolymer has been synthesized by sequential monomer addition to a self-assembled monolayer of (11-(2-bromo-2-methyl)propionyloxy)undecyltrichlorosilane Si/SiO2//polystyrene-b-poly(methyl acrylate)-b-polystyrene (PS-b-PMA-b-PS) and Si/SiO2//PMA-b-PS-b-PMA were prepared by the “grafting from” method using atom transfer radical polymerization The resulting triblock brushes were characterized by ATR−FTIR, water contact angles, ellipsometry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) Free polymer formed during the brush formation was characterized by gel permeation chromatography Treatment of the triblock brushes with block-selective solvents caused reversible changes in the water contact angles and AFM AFM analysis revealed a patterned nanomorphology when the brush was treated with a good solvent for the mid-block We have interpreted this nanomorphology in terms of a folded brush structure where the two end blocks aggregate and force the mid-block to t

Cationic 2,6-bis(imino)pyridine iron and cobalt complexes: synthesis, structures, ethylene polymerisation and ethylene/polar monomer co-polymerisation studies

Abstract: The synthesis and characterisation of a series of cationic bis(imino)pyridine iron and cobalt complexes of the type [LMCl(D)]SbF6 (D = CH3CN or thf) and [LM(R2acac)]SbF6 (R = CH3, CF3, Ph) are described {L = 2,6-bis[1-(2,6-diisopropylphenylimino)ethyl]pyridine, M = Fe or Co}. The solid state structures of these five-coordinate complexes vary between square-based pyramidal and trigonal bipyramidal geometries, depending on the ligands used. Attempts to synthesise cationic metal alkyl complexes of the type [LMR]+ were unsuccessful. However, these complexes serve as highly active ethylene polymerisation catalysts when activated with MAO. Polymerisation activities are comparable to the activities obtained with neutral dichloride precursors [LMCl2] and the resulting polymer properties are nearly identical, suggesting that in all cases the same active species is being generated. The polymerisation activity is not inhibited by the presence of donors such as thf or CH3CN and these cationic precursors can be activated with less co-catalyst than is normally used for neutral dichloride pre-catalysts. As little as 10 equiv. TMA, in combination with 1 equiv. B(C6F5)3, afford a highly active polymerisation system. Co-polymerisation studies of ethylene with polar monomers such as methyl methacrylate (MMA) or styrene resulted in polymer production with high activities. However, in both cases no co-polymer is obtained. The activity of the catalyst is significantly reduced in the presence of methyl acrylate (MA) or 2-vinyl-1,3-dioxolane (VDO) and again no co-polymer is produced. Polar monomers such as vinyl acetate, acrolein and acrylonitrile deactivate the catalyst.

Synthesis of amphiphilic miktoarm ABC star copolymers by RAFT mechanism using maleic anhydride as linking agent

Abstract: The preparation and characterization of amphiphilic ABC miktoarm star copolymers based on polystyrene, and poly(ethylene oxide), poly(methyl acrylate) or poly(N-isopropylacrylamide) blocks are described in this paper. First, macrotransfer agent polySt-MAh-S-C(S)Ph with maleic anhydride and a dithio group at one end of polymer chain was synthesized by the reaction of a dithio group at the end of the polystyrene with maleic anhydride (MAh) in tetrahydrofuran solution. The second, reversible addition−fragmentation chain transfer polymerization of methyl acrylate or N-isopropylacrylamide was carried out in the prescence of polySt-MAh-S-C(S)Ph and benzoyl peroxide. Finally, the anhydride group at the joint of two blocks was reacted with terminal hydroxyl group of poly(ethylene glycol methyl ether). The obtained ABC star copolymers were characterized by 1H NMR spectroscopy and gel permeation chromatography.

Synthesis of Triblock Copolymer Brushes by Surface-Initiated Atom Transfer Radical Polymerization

Abstract: Surface-tethered triblock copolymers composed of poly(methyl acrylate), poly(methyl methacrylate), and poly(2-hydroxyethyl methacrylate) were grown from gold substrates by a series of atom transfer radical polymerizations at ambient temperature. GPC determinations of the molecular weights of desorbed triblock homopolymers suggest that this method can yield relatively homogeneous polymer brushes. To quench polymerization after the synthesis of each block, films were either exposed to a large excess of Cu(II)Br2 or simply rinsed with solvent. Comparison of the thicknesses of multiblock homopolymer films with the thicknesses of films prepared using a single initiation step shows that in the Cu(II) quenching approach >95% of the active chains support growth of an additional block. However, for simple solvent rinsing between blocks, only 85−90% of active chains were preserved during the quenching step.

Chemically induced supramolecular reorganization of triblock copolymer assemblies: Trapping of intermediate states via a shell-crosslinking methodology

Abstract: The mechanism of morphological phase transitions was studied for rod-shaped supramolecular assemblies comprised of a poly(acrylic acid)-block-poly(methyl acrylate)-block-polystyrene (PAA90-b-PMA80-b-PS100) triblock copolymer in 33% tetrahydrofuran/water after perturbation by reaction with a positively charged water-soluble carbodiimide. Tetrahydrofuran solvation of the hydrophobic core domain provided the dynamic nature required for the rod-to-sphere phase transition to be complete within 30 min. The intermediate morphologies such as fragmenting rods and pearl-necklace structures were trapped kinetically by the subsequent addition of a diamino crosslinking agent, which underwent covalent crosslinking of the shell layer. Alternatively, shell-crosslinked rod-shaped nanostructures with preserved morphology were obtained by the addition of the crosslinking agent before the addition of the carbodiimide, which allowed for the shell crosslinking to be performed at a faster rate than the morphological reorganization. The formation of robust shell-crosslinked nanostructures provides a methodology by which the morphological evolution processes can be observed, and it allows access to otherwise thermodynamically unstable nanostructures.

Effect of comonomers on melt processability of polyacrylonitrile

Abstract: This work is concerned with the feasibility of achieving melt-processable polyacrylonitrile copolymer systems as precursors for the manufacture of carbon fibers. Identification of suitable comonomers and achieving the optimum content of the comonomer were some of the main objectives of this investigation. It was seen that methyl acrylate (MA) was found to be suitable for enabling the melt processing of polyacrylonitrile (PAN), in terms of melt viscosity, time stability, and char yield. Below 10 mol % of MA, the PAN copolymer exhibited no flowability, even at very low molecular weights (∼ 20,000). The long-range order inherently present in PAN is speculated to be broken down at a critical value of about 10% MA at 220°C in the PAN-based system, enabling its melt flowability. It was also seen that the incorporation of MA was seen to improve the temperature and molecular weight window of processability of the PAN system. The molecular weight cutoff for the 90/10 mol % acrylonitrile/methyl acrylate (AN/MA) system was about 50,000 at 220°C, whereas it was increased to about 100,000 in the presence of 15 mol % MA comonomer. Feasibility studies on the use of other comonomers such as higher acrylates and acrylamides were also conducted. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 69–83, 2002

Grafting of Poly(alkyl (meth)acrylates) from Swellable Poly(DVB80-co-HEMA) Microspheres by Atom Transfer Radical Polymerization

Abstract: We report the graft polymerization of methyl acrylate (MA), methyl methacrylate (MMA), hydroxyethyl methacrylate (HEMA), and 2-(dimethylamino)ethyl methacrylate (DMAEMA) by atom transfer radical polymerization (ATRP) from lightly cross-linked poly(DVB80-co-HEMA) microspheres. These poly(DVB80-co-HEMA) microspheres were prepared by precipitation copolymerization and subsequently modified by reaction with 2-bromopropionyl bromide to serve as ATRP macroinitiators. MMA, MA, and HEMA were then grafted from these initiator microspheres at room temperature using CuBr/Me4cyclam as catalyst. The graft sites, and hence the grafted polymers, are distributed throughout the initiator microspheres. Addition of a second monomer formed grafted block copolymers, indicating that a significant portion of the first grafts could be reactivated. The final particles represent novel, high-capacity polymer supports comprised of swellable core particles carrying 5.09 and 5.18 mmol/g of grafted poly(DMAEMA) and poly(MMA-b-DMAEMA), ...

Computational insights on the challenges for polymerizing polar monomers.

Abstract: Taking Pd di-imine catalysts as an example, we use first principles density functional theory (B3LYP/6-31G*) to investigate the chain propagation steps for polymerization of polar monomers. We start with the complex formed from insertion of ethylene into the polymer chain and consider insertion into the Pd−C bond for each of four polar monomers: methyl acrylate, vinyl acetate, vinyl chloride, and acrylonitrile. We find 2,1-insertion is favored in each case (by 3 to 5 kcal/mol), resulting in a product with a strong interaction of the polar group for the growing polymer chain with the metal. Next, we insert another unit of the same polar monomer or an ethylene unit (except for acrylonitrile). We optimize the structures for all important intermediates and transition states using a continuum dielectric to account for solvation effects. These studies pinpoint the critical difficulties in designing catalysts to polymerize polar monomers.

Iron-Catalyzed Suspension Living Radical Polymerizations of Acrylates and Styrene in Water1

Abstract: Iron(II)-catalyzed suspension living radical polymerizations of acrylates and styrene have been achieved for the first time in water. In the presence of a large amount of water (water/organic = 1/1 v/v), a half-metallocene type iron complex [Fe(Cp)I(CO)2] induced a smooth polymerization of n-butyl acrylate in conjunction with (CH3)2C(CO2Et)I as an initiator to give polymers of narrow molecular weight distributions (MWDs) (Mw/Mn = 1.2−1.3) and controlled number-average molecular weights, in direct proportion to monomer conversion. Reaching 90% conversion in 4 h, the polymerizations proceeded much faster than in toluene without water. Similarly, methyl acrylate, tert-butyl acrylate, and styrene were polymerized with the same initiating system under aqueous suspension conditions to afford living polymers of controlled molecular weights and narrow MWDs (Mw/Mn = 1.2−1.3). The suspension systems can be applied to the controlled synthesis of block and random copolymers of acrylates and styrene.

Heterogeneous Graft Copolymerization of Chitosan Powder with Methyl Acrylate Using Trichloroacetyl−Manganese Carbonyl Co-initiation

Abstract: A highly deacetylated chitosan powder was successfully trichloroacetylated under heterogeneous conditions. The trichloroacetylated chitosan powder was subsequently graft copolymerized heterogeneously with methyl acrylate using a Mn2(CO)10 co-initiator photoactivated with 436 nm light at room temperature. Reaction products were extracted with acetone in an attempt to separate homopolymer from the grafted powder. Portions of the grafted material (presumably surface grafted chitosan) were also removed from the bulk of the grafted powder. After monitoring the weights of reaction product and total polymer extracted from the reaction product (polymeric extract), gel permeation chromatography was used to resolve the polymeric extract into two separate species, assumed to be the grafted chitosan and homopolymer. With this general technique, graft and homopolymer yields for a series of grafting reactions were obtained. Graft yields greater than 600% (based on a percent weight increase of trunk polymer) were obtain...

Surface modification of polystyrene latex particles via atom transfer radical polymerization

Abstract: The atom transfer radical polymerization (ATRP) technique using the copper halide/ N,N′,N′,N″,N″-pentamethyldiethylenetriamine complex was applied to the graft polymerization of methyl methacrylate and methyl acrylate on the uniform polystyrene (PS) seed particles and formed novel core-shell particles. The core was submicron crosslinked PS particles that were prepared via emulsifier-free emulsion polymerization. The crosslinked PS particles obtained were transferred into the organic phase (tetrahydrofuran), and surface modification using the chloromethylation method was performed. Then, the modified seed PS particles were used to initiate ATRP to prepare a controlled poly(methyl methacrylate) (PMMA) and poly(methyl acrylate) (PMA) shell. The final core-shell particles were characterized using Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning electron microscopy, thermogravimetric analysis, and elementary analysis. The grafting polymerization was conducted successfully on the surface of modified crosslinked PS particles, and the shell thickness and weight ratio (PMMA and PMA) of the particles were calculated. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 892–900, 2002; DOI 10.1002/pola.10160

Modification of waterborne polyurethane by forming latex interpenetrating polymer networks with acrylate rubber

Abstract: Polyurethane (PU)/poly(acrylic rubber) (PAR) latex interpenetrating polymer networks based on waterborne PUs were prepared by sequential polymerization with methyl acrylate, ethyl acrylate, or butyl acrylate. The effect of PU/PAR composition and the cross-linking density in the PAR domain as well as in the PU domain has been studied in terms of density, mechanical, and dynamic mechanical properties in addition to the drying rate and the contact angle of the dispersion cast film with water. A high degree of interpenetrations was verified by mechanical properties showing positive deviation with a maximum from the additivity. In addition, incorporation with acrylate polymers having low glass-transition temperatures effectively augmented the hydrophobicity without sacrificing the elasticity of the original PUs. In addition, the acrylate monomers were polymerized by UV irradiation to significantly reduce the reaction time.

Synthesis and characterization of poly(methyl acrylate) grafted from poly(thiophene) to form solid-state fluorescent materials

Abstract: This paper describes the synthesis and characterization of graft copolymers having a poly(thiophene) (PT) backbone with poly(methyl acrylate) (pMA) sidearms Thiophene monomer containing a protected alcohol group was prepared and polymerized via the McCullough method to yield regioregular PT The backbone was then functionalized to contain an atom-transfer radical polymerization (ATRP) initiator at approximately 90% of the repeat units as determined through 1H NMR analysis, yielding 2,5-poly(3-[1-ethyl-2-(2-bromopropionate)]thiophene) From these initiator sites, MA was polymerized to yield well-defined polymer brushes The addition of the sidearms to the thiophene backbone resulted in twisting of the backbone as a result of steric effects, which caused a decrease in conjugation length of the PT In the solid state, the sidearms trap the PT in a “solution-like” conformation In addition, these arms serve to separate PT chains and disrupt the ordered array usually seen in regioregular PT With a lower conj

Reversible addition-fragmentation chain-transfer (RAFT) copolymerization of vinylidene chloride and methyl acrylate

Abstract: The reversible addition-fragmentation chain-transfer (RAFT) copolymerization of vinylidene chloride and methyl acrylate was investigated at 70°C in benzene. Three dithioesters were synthesized in high yield by a simple and straightforward transesterification method. These dithioesters were successfully used as reversible chain-transfer agents, as demonstrated by the increase of molecular weight with conversion, a relatively low polydispersity index (I p =1.5) in comparison with a blank experiment (J p = 1.9), first-order polymerization kinetics and efficient chain extension. Nevertheless, a transfer reaction to vinylidene chloride monomer was considered to address the limitations of the RAFT process for this system. Moreover, a retardation effect was noticeable on the kinetics, depending on the structure and concentration of the transfer agent, leading to lower rate of polymerization for lower targeted molecular weights.