Radical Polymerization (radical + polymerization)

Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of Radical Polymerization

  • atom transfer radical polymerization
  • atom-transfer radical polymerization
  • controlled radical polymerization
  • conventional radical polymerization
  • free radical polymerization
  • nitroxide-mediated radical polymerization
  • reverse atom transfer radical polymerization
  • surface-initiated atom transfer radical polymerization
  • transfer radical polymerization

  • Terms modified by Radical Polymerization

  • radical polymerization process
  • radical polymerization techniques

  • Selected Abstracts

    Synthesis and Characterization of MoOI2(PMe3)3 and Use of MoOX2(PMe3)3 (X = Cl, I) in Controlled Radical Polymerization

    Jos A. Mata
    Abstract Complex MoOCl2(PMe3)3 smoothly reacts with NaI in acetone to produce MoOI2(PMe3)3 in good yields. The geometry of the compound is mer - cis octahedral, that is, identical to that of the dichloride precursor, as shown by NMR spectroscopy and by an X-ray crystallographic study. Electrochemical investigations of MoOX2(PMe3)3 show irreversible oxidation waves at Ep,a = +0.18 and +0.39 V for X = Cl and I, respectively. A study of the halide exchange between MoOCl2(PMe3)3 and NaI, or between MoOI2(PMe3)3 and Bu4NCl, shows two equilibrated isomers for the mixed halide intermediate MoOICl(PMe3)3. The diiodide complex rapidly exchanges the iodo ligands with chloride upon dissolution in chloroform at room temperature, and with bromide from (1-bromoethyl)benzene (BEB) under more forcing conditions. The equilibrium favors the softer halide (I) on C and the harder one (Cl or Br) on MoIV. Both oxido compounds catalyze the atom transfer radical polymerization (ATRP) of styrene in combination with the BEB initiator, yielding polymers with quite narrow molecular weight distributions (down to 1.11). The apparent polymerization rate constant is approximately doubled in the presence of 1 equiv. of the Al(OiPr)3 cocatalyst. On the other hand, the system is not capable of efficiently controlling the radical chain growth for methyl acrylate polymerization. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Extended X-ray Absorption Fine Structure Study of Copper(I) and Copper(II) Complexes in Atom Transfer Radical Polymerization

    Tomislav Pintauer
    Abstract Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy has been used to investigate structural features of CuIBr and CuIIBr2 complexes with dNbpy, PMDETA, Me6TREN, tNtpy, and Me4CYCLAM in various solvents {dNbpy = 4,4,-bis(5-nonyl)-2,2,-bipyridine, PMDETA = N,N,N,,N,,,N,, -pentamethyldiethylenetriamine, Me6TREN = tris[2-(dimethylamino)ethyl]amine, tNtpy = 4,4,,4,,-tris(5-nonyl)-2,2,:6,,2,,-terpyridine, Me4CYCLAM = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane}. The structures of the CuI and CuII complexes were found to depend on the solvent polarity and the number of nitrogen atoms in the ligand. Generally, in non-polar media and with monomers typically used in ATRP, CuI complexes preferred a tetracoordinate geometry, and were either ionic as observed in [CuI(dNbpy)2]+[CuIBr2], (CuI,NAV = 2.00 , CuI,BrAV = 2.25 ) and [CuI(Me4CYCLAM)]+[CuIBr2], (CuI,NAV = 2.06 , CuI,BrAV = 2.23 ), or neutral as in [CuI(PMDETA)Br] (CuI,NAV = 2.12 , CuI,BrAV = 2.33 ), and [CuI(tNtpy)Br] (CuI,NAV = 2.03 , CuI,BrAV = 2.29 ). The EXAFS analysis of CuIIBr2 complexes indicated a preference for a coordination number of five, such as in [CuII(dNbpy)2Br]+[Br], (CuII,NAV = 2.03 , CuII,BrAV = 2.43 ), [CuII(PMDETA)Br2] (CuII,NAV = 2.03 , CuII,Br1,AV = 2.44 , CuII,Br2,AV = 2.64 ) and [CuII(Me6TREN)Br]+[Br], (CuII,NAV = 2.09 , CuII -BrAV = 2.39 ), with the exception of the neutral tetracoordinate [CuII(dNbpy)Br2] (CuII,NAV = 2.02 , CuII,BrAV = 2.36 ), which has been observed in non-polar media. Additionally, polar media were found to favor bromide dissociation in [CuII(Me6TREN)Br]+[Br], and [CuII(PMDETA)Br2], as indicated by a decrease in the Br and Cu coordination numbers at the Cu- and Br- K -edges, respectively. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

    Functionalization of Chitosan via Atom Transfer Radical Polymerization for Gene Delivery

    Yuan Ping
    Abstract It is of crucial importance to modify chitosan-based polysaccharides in the designing of biomedical materials. In this work, atom transfer radical polymerization (ATRP) was employed to functionalize chitosan in a well-controlled manner. A series of new degradable cationic polymers (termed as PDCS) composed of biocompatible chitosan backbones and poly((2-dimethyl amino)ethyl methacrylate) (P(DMAEMA)) side chains of different length were designed as highly efficient gene vectors via ATRP. These vectors, termed as PDCS, exhibited good ability to condense plasmid DNA (pDNA) into nanoparticles with positive charge at nitrogen/phosphorus (N/P) ratios of 4 or higher. All PDCS vectors could well protect the condensed DNA from enzymatic degradation by DNase I and they displayed high level of transfectivity in both COS7, HEK293 and HepG2 cell lines. Most importantly, in comparison with high-molecular-weight P(DMAEMA) and ,gold-standard' PEI (25 kDa), the PDCS vectors showed considerable buffering capacity in the pH range of 7.4 to 5, and were capable of mediating much more efficient gene transfection at low N/P ratios. At their own optimal N/P ratios for trasnsfection, the PDCS/pDNA complexes showed much lower cytotoxicity. All the PDCS vectors were readily to be degradable in the presence of lysozyme at physiological conditions in vitro. These well-defined PDCS polymers have great potentials as efficient gene vectors in future gene therapy. [source]

    Organic Thin Film Transistors with Polymer Brush Gate Dielectrics Synthesized by Atom Transfer Radical Polymerization

    C. Pinto
    Abstract Low operating voltage is an important requirement that must be met for industrial adoption of organic field-effect transistors (OFETs). We report here solution fabricated polymer brush gate insulators with good uniformity, low surface roughness and high capacitance. These ultra thin polymer films, synthesized by atom transfer radical polymerization (ATRP), were used to fabricate low voltage OFETs with both evaporated pentacene and solution deposited poly(3-hexylthiophene). The semiconductor-dielectric interfaces in these systems were studied with a variety of methods including scanning force microscopy, grazing incidence X-ray diffraction and neutron reflectometry. These studies highlighted key differences between the surfaces of brush and spun cast polymethyl methacrylate (PMMA) films. [source]

    CdS-Nanoparticle/Polymer Composite Shells Grown on Silica Nanospheres by Atom-Transfer Radical Polymerization,

    T. Cui
    Abstract In this paper we describe the combined use of surface-initiated atom transfer radical polymerization (ATRP) and a gas/solid reaction in the direct preparation of CdS-nanoparticle/block-copolymer composite shells on silica nanospheres. The block copolymer, consisting of poly(cadmium dimethacrylate) (PCDMA) and poly(methyl methacrylate) (PMMA), is obtained by repeatedly performing the surface-initiated ATRP procedures in N,N -dimethylformamide (DMF) solution at room temperature, using cadmium dimethacrylate (CDMA) and methyl methacrylate (MMA) as the monomers. CdS nanoparticles with an average size of about 3,nm are generated in situ by exposing the silica nanospheres coated with block-copolymer shells to H2S gas. These synthetic core,shell nanospheres were characterized using transmission electron microscopy (TEM), dynamic light scattering (DLS), thermogravimetric analysis (TGA), diffuse reflectance UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), and powder X-ray diffraction (XRD). These composite nanospheres exhibit strong red photoluminescence in the solid state at room temperature. [source]

    New Iron(II) Complexes for Atom-Transfer Radical Polymerization: The Ligand Design for Triazacyclononane Results in High Reactivity and Catalyst Performance

    Mitsunobu Kawamura
    Abstract Mononuclear cordinatively unsaturated iron(II) complexes having a triazacyclononane ligand were developed as highly efficient and environmentally friendly catalysts for the atom-transfer radical polymerization (ATRP). These iron catalysts showed high performance in the well-controlled ATRP of styrene, methacrylates, and acrylates. The high reactivity of these catalysts led to well-controlled polymerization and block copolymerization even with lower catalyst concentrations. [source]

    A Bimetallic Ruthenium Complex as a Catalyst Precursor for the Atom Transfer Radical Polymerization of Methacrylates at Ambient Temperature

    Michel Haas
    Abstract The bimetallic ruthenium complex [(1,3,5- i -Pr3C6H3)Ru(,-Cl)3RuCl(C2H4)(PCy3)] has been synthesized by reaction of [(1,3,5- i -Pr3C6H3)RuCl2)]2 with one equivalent of PCy3 in the presence of ethylene. It can be used as a catalyst precursor for the controlled atom transfer radical polymerization of methacrylates at 35,C. The resulting polymers show low polydispersities. [source]

    Preparation of gradient copolymers via ATRP using a simultaneous reverse and normal initiation process.


    Abstract Spontaneous gradient copolymers were prepared in both bulk and miniemulsion systems via Atom Transfer Radical Polymerization (ATRP) utilizing a Simultaneous Reverse and Normal Initiation (SR & NI) process. Both instantaneous and cumulative compositions were used to characterize the gradient copolymers. The gradient copolymers were obtained with an array of gradient compositions ranging from a subtle to strong variation in monomer distribution along the polymer backbones, depending on the ratio of comonomers initially added to the copolymerization system. The compositions of the gradient copolymer produced in miniemulsion systems were similar to those generated in bulk. 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3616,3622, 2005 [source]

    Fluorinated Polymer Nanoparticles as a Novel 19F MRI Contrast Agent Prepared by Dendrimer-Initiated Living Radical Polymerization

    Michihiro Ogawa
    Abstract Novel fluorinated polymer nanoparticles (PNPs) for 19F MRI were prepared by living radical polymerization initiated by a dendrimer. The dendritic macroinitiator with Br substituents was synthesized from hydroxy-group-terminated G2 polyamidoamine dendrimers. The arborescent fluorinated polymers of 2,2,3,3-tetrafluoropropyl methacrylate and 2,2,2-trifluoroethyl methacrylate were characterized in molecular weight, the number of arms, the degree of polymerization per arm, and the diameter as a whole. The PNP diameter was precisely controlled by the molecular weight in the range of 3,25,nm. In addition, the fluorinated PNP gave a narrow resonance by 19F NMR spectroscopy. These results indicate that the fluorinated PNP can be used as a new type of 19F MRI agent. [source]

    Synthesis of Polystyrene- block -Poly(methyl methacrylate) with Fluorene at the Junction: Sequential Anionic and Controlled Radical Polymerization from a Single Carbon

    Nathan D. Contrella
    Abstract Polystyrene- block -poly(methyl methacrylate) (PS- b -PMMA) has been synthesized by sequential anionic and reverse atom transfer radical polymerization (ATRP) or a variation of nitroxide mediated polymerization (NMP) from a single initiating site, specifically the 9-carbon on 2,7-dibromofluorene or fluorene. The addition of the second arm (PS) relied on thermal decomposition of 2,2,-azoisobutyronitrile (AIBN) to generate radicals, abstracting the 9-H on the polymer-bound fluorene species to form the initiating radical. Styrene was not present in the reaction mixture when AIBN was decomposed, preventing competition between addition across the monomeric alkene and hydrogen abstraction from the fluorene. After 1,h, styrene was introduced and mediation of the subsequent radical polymerization was achieved by the presence of CuCl2/ligand or TEMPO. Characterization of the diblock copolymers by gel permeation chromatography (GPC) revealed substantial shifts in number average molecular weight () values compared to the anionically prepared PMMA macroinitiator, while polydispersity indices (PDI's) remained relatively low (typically,<,1.5). Characterization by UV detection with GPC (at 310,nm) verified that the diblock polymer is chromophore-bound, which was further verified by UV-vis spectroscopy of the isolated diblock. [source]

    Nitroxide-Mediated Radical Polymerization of N - tert -Butylacrylamide

    Orla Gibbons
    Abstract The nitroxide-mediated polymerization of N - tert -butylacrylamide (TBAM) in DMF at 120,C using SG1/DEPN and AIBN has been investigated. Linear growth in number-average molecular weight () versus conversion and narrow molecular weight distributions (MWDs) with high livingness were obtained up to ,8,000 g,,mol,1. For higher molecular weights, the MWDs gradually became broader with low molecular weight tailing, and deviated downwards from theoretical values. Quantitative analyses of MWDs, along with specifically designed conventional radical polymerizations at 120,C, were consistent with chain transfer to monomer limiting the attainable . This finding can be equally applied to existing literature polymerizations of TBAM. [source]

    Atom Transfer Radical Polymerization and Third-Order Nonlinear Optical Properties of New Azobenzene-Containing Side-Chain Polymers

    Najun Li
    Abstract The atom transfer radical polymerization (ATRP) technique has been successfully applied to synthesize a series of nonlinear optically (NLO) active homopolymers, 4-(4-nitrophenyl-diazenyl) phenyl acrylate (P - NPAPA) and 4-(4-methoxyphenyl-diazenyl) phenyl acrylate (P - MPAPA), containing azobenzene groups on the side chain. The third-order NLO properties of the polymer films were measured by the degenerated four-wave mixing (DFWM) technique. A dependence of the ,(3) values and response times of polymers on their number-average molecular weight and the electronic effect of the substituent (nitro- or methoxy-) on the azobenzene group have been evidenced. The increasing ,(3) value of the polymer films at the magnitude of about 10,10 was displayed with increasing molecular weight and the presence of the push-pull electronic system contributes much in enhancing the third-order NLO susceptibility of polymers. [source]

    Synthesis and Characterization of Styrene/Butyl Acrylate Linear and Star Block Copolymers via Atom Transfer Radical Polymerization

    Jinyu Huang
    Abstract Summary: Well-defined styrene (S) and butyl acrylate (BA) linear and star-like block copolymers are synthesized via atom transfer radical polymerization (ATRP) using di- and trifunctional alkyl halide initiators employing the Cu/PMDETA (N,N,N,,N,,N,-pentamethyldiethylenetriamine) catalyst system. Initial addition of CuII deactivator and utilization of halogen exchange techniques suppresses the coupling of radicals and improves cross-propagation to a large extent, which results in better control over the polymerization. Two types of star-like PBA/PS block copolymers are prepared by using core-first techniques: a trifunctional PBA or PS macroinitiator extended with the other monomer. Block copolymers with a well-defined structure and low polydispersity (PDI,=,) are obtained in both cases. A trifunctional PBA3 macroinitiator with ,=,136,000 g,,mol,1 and PDI,=,1.15 is extended to (PBA-PS)3 star-like block copolymer with ,=,171,100 g,,mol,1 and PDI,=,1.15. A trifunctional PS3 macroinitiator with ,=,27,000 g,,mol,1 and PDI,=,1.16 g,,mol,1 is extended to (PS-PBA)3 with ,=,91,500 g,,mol,1 and PDI,=,1.40. The individual star-like macromolecules as well as their aggregates are visualized by atomic force microscopy (AFM) where the PS and PBA adopt the globular and extended conformation, respectively. For the PBA core star block copolymers, PS segments tend to aggregate either intramolecularly or intermolecularly. PS core star block copolymers form aggregates with a PS core and emanating PBA chains. Most aggregates have ,n,,3' arms but minor amounts of ,defective' stars with 4, 5, 8, or 11 arms are also observed. The AFM analysis shows that PS core star block copolymers contain about 92% three-arm block copolymers, and the efficiency of cross-propagation is 97.3%. Schematic representation of the synthesis of BA/S star-like block copolymers by ATRP, and their resultant AFM images. [source]

    Clay-PMMA Nanocomposites by Photoinitiated Radical Polymerization Using Intercalated Phenacyl Pyridinium Salt Initiators

    Alper Nese
    Abstract Summary: In situ synthesis of poly(methyl methacrylate) (PMMA) nanocomposites by photopolymerization using organophilic montmorillonite (MMT) as the layered clay is reported. MMT clay was ion exchanged with N -phenacyl, N,N -dimethylanilinium hexafluoro phosphate (PDA) which acts as both suitable intercalant- and photo-initiator. These modified clays were then dispersed in methyl methacrylate (MMA) monomer in different loading degrees to carry out the in situ photopolymerization. Intercalation ability of the photoinitiator and exfoliated nanocomposite structure were evidenced by both X-ray diffraction (XRD) spectroscopy and transmission electron microscopy (TEM). Thermal properties and morphologies of the resultant nanocomposites were also studied. Schematic representation of clay-PMMA nanocomposites by photoinitiated radical polymerization. [source]

    Atom-Transfer Radical Polymerization: A Strategy for the Synthesis of Halogen-Free Amino-Functionalized Poly(methyl methacrylate) in a One-Pot Reaction

    Veera Bhadraiah Sadhu
    Abstract Summary: An initiator containing an alkyl bromide unit and a protected amine functional group is used with CuBr/N,N,N,,N,,N,-pentamethyldiethylenetriamine (PMDETA), in a 1:2 molar ratio with respect to initiator concentration, in order to obtain amino-group terminated as well as halogen-free poly(methyl methacrylate) (PMMA) in a one-pot atom-transfer radical polymerization (ATRP). The terminal bromines are replaced by hydrogen atoms of the PMDETA ligand, which acts as a transfer agent. However, terminating side reactions like disproportionation or dehydrobromination occur from the beginning of the polymerization. Kinetic studies by in-line Raman spectroscopy and off-line 1H NMR spectroscopy revealed that the controlled character of the ATRP is lost under these conditions. The measured molecular weights were consistently higher than the theoretical ones and the molecular weight distributions are relatively broad. Thermal analysis of the obtained poly(methyl methacrylate) shows two main degradation steps, one starting from unsaturated end groups (depolymerization), and one caused by main-chain scission, a further proof for the occurrence of terminating side reactions. Structural analysis of PMMA by matrix-assisted laser desorption-ionization mass spectrometry. [source]

    Atom Transfer Radical Polymerization of Glycidyl Methacrylate: A Functional Monomer

    Pedro Francisco Caamero
    Abstract Summary: A detailed investigation of the polymerization of glycidyl methacrylate (GMA), an epoxy-functional monomer, by atom transfer radical polymerization (ATRP) was performed. Homopolymers were prepared at relatively low temperatures using ethyl 2-bromoisobutyrate (EBrIB) as the initiator and copper halide (CuX) with N,N,N,,N,,N,-pentamethyldiethylenetriamine (PMDETA) as the catalyst system. The high polymerization rate in the bulk did not permit polymerization control. However, homopolymerization in solution enabled us to explore the effects of different experimental parameters, such as temperature, solvent (toluene vs. diphenyl ether) and initiator concentration, on the controllability of the ATRP process. SEC analysis of the homopolymers synthesized confirmed the importance of solvent character on molecular weight control, the lowest polydispersity indices () and the highest efficiencies being found when the polymerizations were performed in diphenyl ether in combination with a mixed halide technique. A novel poly(glycidyl methacrylate)- block -poly(butyl acrylate) (PGMA- b -PBA) diblock copolymer was prepared through ATRP using PGMA-Cl as a macro-initiator. This chain growth experiment demonstrated a good living character under the conditions employed, while simultaneously indicating a facile synthetic route for this type of functional block copolymer. In addition, the isotacticity parameter for the PGMAs obtained was estimated using 1H NMR analysis which gave a value of ,GMA,=,0.26 in agreement with that estimated in conventional radical polymerization. SEC chromatograms of PGMA-Cl macroinitiator and PGMA- b -PBA diblock copolymer. [source]

    Controlled Radical Polymerization of Vaporized Vinyl Monomers on Solid Surfaces under UV Irradiation

    Mikio Yasutake
    Abstract Summary: In order to prepare well-defined polymers on solid surfaces in the gas phase, a gas phase-assisted surface polymerization (GASP) of vinyl monomers was carried out on solid surfaces pre-coated with a photoiniferter, 2-cyanoprop-2-yl N,N,-dimethyldithiocarbamate, under UV irradiation. The GASP of methyl methacrylate (MMA) resulted in the formation of polymer on the surfaces and showed a proportional relationship between and polymer yield. Consecutive copolymerization of MMA and styrene led to the formation of a block copolymer, which was confirmed by a selective solvent fractionation method. These results demonstrate that controlled radical polymerization of vaporized monomer occurred on the solid surfaces. Expected mechanism of GASP under UV irradiation. [source]

    Physical Properties of PBMA- b -PBA- b -PBMA Triblock Copolymers Synthesized by Atom Transfer Radical Polymerization

    Luis Martn-Gomis
    Abstract The physical properties of well-defined poly(butyl methacrylate)- block -poly(butyl acrylate)- block -poly(butyl methacrylate) (PBMA- b -PBA- b -PBMA) triblock copolymers synthesized by atom transfer radical polymerization (ATRP) are reported. The glass transition and the degradation temperature of copolymers were determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). DSC measurements showed phase separation for all of the copolymers with the exception of the one with the shortest length of either inner or outer blocks. TGA demonstrated that the thermal stability of triblock copolymers increased with decreasing BMA content. Dynamic mechanical analysis was used for a preceding evaluation of adhesive properties. In these block copolymers, the deformation process under tension can take place either homogeneously or by a neck formation depending on the molecular weight of the outer BMA blocks and on the length of the inner soft BA segments. Microindentation measurements were also performed for determining the superficial mechanical response and its correlation with the bulk behavior. Stress-strain curves for the different PBMA- b -PBA- b -PBMA specimens at room temperature and at 10 mm/min. [source]

    Concurrent Initiation by Air in the Atom Transfer Radical Polymerization of Methyl Methacrylate

    Ajaya Kumar Nanda
    Abstract The effect of air in atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was studied. Air initiated polymerization was clearly noticed by the appearance of a low molecular weight peak in the synthesis of high molecular weight poly(isobutylene)- graft -poly(methyl methacrylate) (Mn,=,5.0,,105 g/mol). The concentration of chains initiated by oxygen (air) was ,8,,10,4 mol/L, determined using the Gladstone-Dale relationship. The tentatively proposed mechanism for air initiated polymerization was supported by kinetic studies. Similar to typical ATRP systems, the rate of air initiated polymerization increased with temperature, [MMA], amount of air, and activity of the catalyst complex. Polymers with lower polydispersities (Mw/Mn,=,1.13) were obtained in the presence of Cu(II) as compared to Cu(I) catalyst complex system. Kinetic plots for the air initiated bulk polymerization of MMA at (,) 20,C, (,) 50,C, and (,) 90,C. [source]

    A Novel Route to Multiphase Polymer Systems Containing Nano-Droplets: Radical Polymerization of Vinylic Monomers in Gelled Water-in-Oil Miniemulsions

    Christian Holtze
    Abstract Summary: A new strategy for the synthesis of composite polymers with larger volume fraction of aqueous inclusions less than 1 m in diameter is presented. A water-in-oil miniemulsion of aqueous droplets in a continuous, cross-linkable monomer phase is prepared. The addition of an organo-gelator allows the immobilization of the droplets in a solid gel, thus avoiding the usual demixing upon polymerization of the continuous phase. This pregelled system is then converted into a composite polymer by photoinitiated free radical polymerization. Such coatings may be used for an improved climate control of buildings or as a deposit for the controlled release of actives from polar nano-droplets. SEM image of a cross-linked composite polymer showing controlled droplet inclusions with a maximal diameter of 500 nm. [source]

    A Novel Process for Ultrasound-Induced Radical Polymerization in CO2 -Expanded Fluids

    Maartje F. Kemmere
    Abstract Summary: A strong viscosity increase upon polymerization hinders cavitation and subsequent radical formation during an ultrasound-induced bulk polymerization. In this work, ultrasound-induced radical polymerizations of methyl methacrylate (MMA) have been performed in CO2 -expanded MMA in order to reduce the viscosity of the reaction mixture. For this purpose, the phase behavior of CO2/MMA systems has been determined. With temperature oscillation calorimetry, the influence of CO2 on the viscosity and on the reaction kinetics of ultrasound-induced polymerizations of MMA has been studied. In contrast to polymerizations in bulk, this technique shows that a low viscosity is maintained during polymerization reactions in CO2 -expanded MMA. As a consequence, a constant or even increasing polymerization rate is observed when pressurized CO2 is applied. Moreover, the ultrasound-induced polymer scission in CO2 -expanded MMA is demonstrated, which appears to be a highly controlled process. Finally, a preliminary sustainable process design is presented for the production of 10 kg/h pure PMMA (specialty product) in CO2 -expanded MMA by ultrasound-induced initiation. Process flow diagram of the ultrasound-induced polymerization of MMA in CO2 -expanded MMA. [source]

    Acrylonitrile-Butadiene Rubber (NBR) Prepared via Living/Controlled Radical Polymerization (RAFT)

    Andreas Kaiser
    Abstract In the current work we present results on the controlled/living radical copolymerization of acrylonitrile (AN) and 1,3-butadiene (BD) via reversible addition fragmentation chain transfer (RAFT) polymerization techniques. For the first time, a solution polymerization process for the synthesis of nitrile butadiene rubber (NBR) via the use of dithioacetate and trithiocarbonate RAFT agents is described. It is demonstrated that the number average molar mass, , of the NBR can be varied between a few thousand and 60,000,g,,mol,1 with polydispersities between 1.2 and 2.0 (depending on the monomer to polymer conversion). Excellent agreement between the experimentally observed and the theoretically expected molar masses is found. Detailed information on the structure of the synthesized polymers is obtained by variable analytical techniques such as infrared spectroscopy (IR), nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry, and electrospray ionization-mass spectrometry (ESI-MS). [source]

    EPR Analysis of n -Butyl Acrylate Radical Polymerization

    Johannes Barth
    Abstract Via electron paramagnetic resonance (EPR) spectroscopy, concentrations of secondary propagating radicals (SPRs) and tertiary mid-chain radicals (MCRs) in n -butyl acrylate solution polymerization were measured. The EPR spectrum is dominated by the 4-line spectrum of SPRs at ,50,C and by the 7-line spectrum of MCRs at +70,C. At intermediate temperatures, a third spectral component is seen, which is assigned to an MCR species with restricted rotational mobility. The MCR components are produced by 1,5-hydrogen shift (backbiting) of SPRs. The measured ratio of MCRs to SPRs allows for estimating the rate coefficient k for monomer addition to a mid-chain radical. For 70,C, k is obtained to be 65.5 L,,mol,1,,s,1. [source]

    New Strategy Targeting Well-Defined Polymethylene- block -Polystyrene Copolymers: The Combination of Living Polymerization of Ylides and Atom Transfer Radical Polymerization

    Jian-Zhuang Chen
    Abstract Well-defined polymethylene- block -polystyrene (PM- b -PS) diblock copolymers were synthesized via a combination of living polymerization of ylides and atom transfer radical polymerization (ATRP) of styrene. A series of hydroxyl-terminated polymethylenes (PM-OHs) with different molecular weight and narrow molecular weight distribution were prepared using living polymerization of ylides following efficient oxidation in a quantitive functionality. Then, the macroinitiators (PM-MIs (,=,1,900,15,000; PDI,=,1.12,1.23)) transformed from PM-OHs in ,,100% conversion initiated ATRPs of styrene to construct PM- b -PS copolymers. The GPC traces indicated the successful extension of PS segment ( of PM- b -PS,=,5,000,41,800; PDI,=,1.08,1.23). Such copolymers were characterized by 1H NMR and DSC. [source]

    Synthesis of Well-Defined Rod-Coil Diblock Copolymer of Aromatic Polyether and Polyacrylonitrile by Chain-Growth Condensation Polymerization and Atom Transfer Radical Polymerization

    Naomi Ajioka
    Abstract The synthesis of diblock copolymers of aromatic polyether and polyacrylonitrile (PAN) was conducted by chain-growth condensation polymerization (CGCP) and atom transfer radical polymerization (ATRP) from an orthogonal initiator. When CGCP for aromatic polyether was carried out from a PAN macroinitiator obtained by ATRP with an orthogonal initiator, decomposition of the PAN backbone occurred. However, when ATRP of acrylonitrile was conducted from an aromatic polyether macroinitiator obtained by CGCP followed by introduction of an ATRP initiator unit, the polymerization proceeded in a well-controlled manner to yield aromatic polyether- block -polyacrylonitrile (polyether- b -PAN) with low polydispersity. This block copolymer self-assembled in N,N -dimethylformamide to form bundle-like or spherical aggregates, depending on the length of the PAN units in the block copolymer. [source]

    Water-Soluble Carbon Nanotubes by Redox Radical Polymerization

    Dimitrios Tasis
    Abstract Water-soluble single- and multi-walled carbon nanotubes (CNTs) were prepared by grafting polyacrylamide chains from the graphitic surface via ceric ion-induced redox radical polymerization. The reducing functionalities were covalently attached to the tubes by peroxide-assisted radical reaction. The results showed that polymer chains were grafted onto CNTs by the redox process. The redox radical polymerization initiated by carbon nanotube-bearing functionalities not only provides a powerful strategy for modifying the carbon nanostructures but also gives us the knowledge of their sidewall chemistry. [source]

    Fabrication of Chemically Tethered Binary Polymer-Brush Pattern through Two-Step Surface-Initiated Atomic-Transfer Radical Polymerization

    Feng Zhou
    Abstract Summary: The communication provides a novel and alternative route to generate chemically tethered binary polymer-brush pattern through two-step surface-initiated atomic-transfer radical polymerization (SI-ATRP). Polymer brush-1 was prepared by SI-ATRP, passivated by a reaction with NaN3, and etched with UV irradiation through a transmission electron microscopy grid to create exposed sites for the subsequently attached initiator on which polymer brush-2 was grown. Schematic representation of the resultant binary polymer brush patterns. [source]

    Chain Transfer and Efficiency of End-Group Introduction in Free Radical Polymerization of Methyl Methacrylate in the Presence of Poly(methyl methacrylate) Macromonomer

    Kazuki Miyake
    Abstract Summary: Experimental and modeling studies of addition,fragmentation chain transfer (AFCT) during radical polymerization of methyl methacrylate in the presence of poly(methyl methacrylate) macromonomer with 2-carbomethoxy-2-propenyl , -ends (PMMA-CO2Me) at 60,C are reported. The results revealed that AFCT involving PMMA-CO2Me formed in situ during methyl methacrylate polymerization has a negligible effect on the molecular weight distribution. [source]

    Synthesis of Polymer Brushes Using Atom Transfer Radical Polymerization

    Jeffrey Pyun
    Abstract Atom transfer radical polymerization (ATRP) is a robust method for the preparation of well-defined (co)polymers. This process has also enabled the preparation of a wide range of polymer brushes where (co)polymers are covalently attached to either curved or flat surfaces. In this review, the general methodology for the synthesis of polymer brushes from flat surfaces, polymers and colloids is summarized focusing on reports using ATRP. Additionally, the morphology of ultrathin films from polymer brushes is discussed using atomic force microscopy (AFM) and other techniques to confirm the formation of nanoscale structure and organization. Formation of polymer brushes by ATRP. [source]

    Kinetics and Molecular Weight Development of Dithiolactone-Mediated Radical Polymerization of Styrene

    Jess Guillermo Soriano-Moro
    Abstract Calculations of polymerization kinetics and molecular weight development in the dithiolactone-mediated polymerization of styrene at 60,C, using 2,2,-azobisisobutyronitrile (AIBN) as initiator and , -phenyl- , -butirodithiolactone (DTL1) as controller, are presented. The calculations were based on a polymerization mechanism based on the persistent radical effect, considering reverse addition only, implemented in the PREDICI commercial software. Kinetic rate constants for the reverse addition step were estimated. The equilibrium constant (K,=,kadd/k -add) fell into the range of 105,106 L,,mol,1. Fairly good agreement between model calculations and experimental data was obtained. [source]