Distribution by Scientific Domains
Distribution within Polymers and Materials Science

Kinds of ATRP

  • normal atrp

  • Terms modified by ATRP

  • atrp system

  • 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]

    Polymers from renewable resources: Bulk ATRP of fatty alcohol-derived methacrylates

    Gkhan ayli
    Abstract Copper-mediated atom transfer radical polymerization (ATRP) of lauryl methacrylate (LMA) and other long-chain methacrylates was investigated in bulk at 35,C by using CuCl/N,N,N,,N,,N,, -pentamethyldiethylenetriamine (PMDETA)/tricaprylylmethylammonium chloride (Aliquat336) as the catalyst system and ethyl 2-bromoisobutyrate (EBIB) as the initiator. The investigated monomers can be derived from fatty alcohols and are therefore an important renewable resource for a sustainable development of our future. The amounts of ligand, Aliquat336 and CuCl were optimized and the effect of their concentrations on the control of the polymerization and the observed conversions were investigated. It was found that a molar ratio of EBIB/CuCl/Ligand/Aliquat336 of 1,:,1,:,3,:,1 provided the highest conversions of LMA and the best controlled polymerizations. These optimized conditions allowed for the synthesis of poly(lauryl methcarylate)s with different targeted DP (25, 50, 75, 100, 120, 240, and 500), including high-molecular-weight polymers with narrow molecular weight distributions. In addition, methacrylate monomers were prepared from fatty alcohols (capric, myristic, palmitic, stearic) and polymerized using the developed procedure to obtain polymers with the same DP and different chain lengths (C10, C12, C14, C16, and C18) of pending alkyl groups. Finally, the thermal properties of these polymers were examined by differential scanning calorimetry and thermogravimetric analysis. [source]

    Synthesis, Morphology, and Properties of Poly(3-hexylthiophene)- block -Poly(vinylphenyl oxadiazole) Donor,Acceptor Rod,Coil Block Copolymers and Their Memory Device Applications

    Yi-Kai Fang
    Abstract Novel donor,acceptor rod,coil diblock copolymers of regioregular poly(3-hexylthiophene) (P3HT)- block -poly(2-phenyl-5-(4-vinylphenyl)-1,3,4-oxadiaz-ole) (POXD) are successfully synthesized by the combination of a modified Grignard metathesis reaction (GRIM) and atom transfer radical polymerization (ATRP). The effects of the block ratios of the P3HT donor and POXD pendant acceptor blocks on the morphology, field effect transistor mobility, and memory device characteristics are explored. The TEM, SAXS, WAXS, and AFM results suggest that the coil block fraction significantly affects the chain packing of the P3HT block and depresses its crystallinity. The optical absorption spectra indicate that the intramolecular charge transfer between the main chain P3HT donor and the side chain POXD acceptor is relatively weak and the level of order of P3HT chains is reduced by the incorporation of the POXD acceptor. The field effect transistor (FET) hole mobility of the system exhibits a similar trend on the optical properties, which are also decreased with the reduced ordered P3HT crystallinity. The low-lying highest occupied molecular orbital (HOMO) energy level (,6.08 eV) of POXD is employed as charge trap for the electrical switching memory devices. P3HT- b -POXD exhibits a non-volatile bistable memory or insulator behavior depending on the P3HT/POXD block ratio and the resulting morphology. The ITO/P3HT44 - b - POXD18/Al memory device shows a non-volatile switching characteristic with negative differential resistance (NDR) effect due to the charge trapped POXD block. These experimental results provide the new strategies for the design of donor-acceptor rod-coil block copolymers for controlling morphology and physical properties as well as advanced memory device applications. [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]

    Thermosensitive Nanostructures Comprising Gold Nanoparticles Grafted with Block Copolymers,

    D. Li
    Abstract Binary thermosensitive nanocomposites are fabricated by grafting block copolymers of poly(N -isopropylacrylamide) and poly(methoxy-oligo(ethylene glycol) methacrylate) onto gold nanoparticles through consecutive, surface-initiated, atom-transfer radical polymerization (ATRP). These Au@copolymer nanocomposites display a well-defined core/shell nanostructure and have two thermosensitive points near 33 and 55,C in an aqueous suspension corresponding to the thermally induced conformational transition of inner homopolymer segments and outer oligo(ethylene glycol)-containing copolymer layer, respectively. Silver nanoparticles trapped within Au@copolymer nanocomposites with weakly crosslinked shells display thermally modulated catalytic activity as heterogeneous catalysts because of the thermosensitive collapse of the polymer layers. [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]

    Hyperbranched Polymers for Photolithographic Applications , Towards Understanding the Relationship between Chemical Structure of Polymer Resin and Lithographic Performances

    ADVANCED MATERIALS, Issue 10-11 2009
    Christos L. Chochos
    A chemically amplified resist based on a hyperbranched polymer resin is demonstrated for the first time. The hyperbranched polymer is synthesized using the atom-transfer radical polymerization (ATRP) technique, and resists prepared from this hyperbranched polymer present good pattern profiles and line-edge roughness (3,) values comparable to those of the reference (commercial) resist. [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]

    Synthesis of Schiff Base-Ruthenium Complexes and Their Applications in Catalytic Processes

    Renata Drozdzak
    Abstract The synthesis of various Schiff base mononuclear and binuclear ruthenium complexes, whose additional ligands around the metal core have been selected from an array of motifs, is described. These types of ruthenium complexes, conveniently prepared from commonly available ruthenium sources, are rather stable, display good tolerance towards diverse organic functionalities and also to air and moisture. Remarkably, they exhibit a high activity and chemoselectivity in a variety of catalytic processes such as ring-closing metathesis (RCM), Kharasch addition, alkyne dimerization, enol ester synthesis, ring-opening metathesis polymerization (ROMP) and atom-transfer radical polymerization (ATRP). This review covers both homogeneous and heterogeneous hybrid Schiff base-ruthenium complexes. [source]

    Preparation of polyacrylonitrile with improved isotacticity and low polydispersity

    Jianguo Jiang
    Abstract The preparation of a polymer with both low polydispersity and high tacticity is one current challenge we face and warrants thorough investigation from both the theoretical and experimental standpoints. In this study, we synthesized polyacrylonitrile (PAN) with simultaneously controlled molecular weight and tacticity on the basis of the strategy of the atom transfer radical polymerization (ATRP) of acrylonitrile (AN) in the presence of Lewis acids. A new combined initiation system of 3-bromopropionitrile (3-BPN)/Cu2O/N,N,N,,N,-tetramethylethylenediamine (TMEDA) was used for the ATRP of AN for the first time. When the polymerization was performed with the ratio [AN]0/[Initiator]0/[Cu2O]0/[TMEDA]0 = 190/1/0.5/1.5 (where the subscript 0 indicates the initial conditions) in ethylene carbonate at 60C for 48 h, the polydispersity of the obtained PAN was 1.13, and the molecular weight was up to 13,710. The polymerization kinetics results show that the polymerizations proceeded with a living/controlled nature except that an induction period existed during the polymerization process because of the lower initiating activity of 3-BPN. Also, two kinds of Lewis acid, AlCl3 and yttrium trifluororomethanesulflnate, were used in the ATRP system of AN for the tacticity control. The addition of 0.01 equiv (relative to AN) of the Lewis acid AlCl3 in the polymerization afforded PAN with an improved isotacticity [meso/meso triad (mm) = 0.32] and a very narrow polydispersity (1.06). 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

    Thermal decomposition kinetics of poly(nButMA- b -St) diblock copolymer synthesized by ATRP

    Adnan KurtArticle first published online: 8 JUN 200
    Abstract The reaction mechanism of decomposition process and the kinetic parameters of the poly(n -butyl methacrylate-b-styrene), poly(nButMA-b-St), diblock copolymer synthesized by atom transfer radical polymerization (ATRP) were investigated by thermogravimetric analysis (TGA) at different heating rates. TGA curves showed that the thermal decomposition occurred in one stage. The apparent activation energies of thermal decomposition for copolymer, as determined by the Kissinger's, Flynn,Wall,Ozawa and Tang methods, which does not require knowledge of the reaction mechanism (RM), were 112.52, 116.54, and 113.41 kJ/mol, respectively. The experimental results were compared with master plots, in the range of the Doyle approximation. Analysis of experimental results suggests that in the conversion range studied, 3,18%, the actual RM is an A2 sigmoidal type. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

    Microphase separation behavior on the surfaces of poly(dimethylsiloxane)- block -poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate) diblock copolymer coatings

    Zheng-Hong Luo
    Abstract Microphase separation behavior on the surfaces of poly(dimethylsiloxane)- block -poly(2,2,3,3,4,4,4-heptafluorobutyl methacrylate) (PDMS- b -PHFBMA) diblock copolymer coatings was investigated. The PDMS- b -PHFBMA diblock copolymers were successfully synthesized via atom transfer radical polymerization (ATRP). The chemical structure of the copolymers was characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. Surface composition was studied by X-ray photoelectron spectroscopy. Copolymer microstructure was investigated by atomic force microscopy. The microstructure observations show that well-organized phase-separated surfaces consist of hydrophobic domain from PDMS segments and more hydrophobic domain from PHFBMA segments in the copolymers. The increase in the PHFBMA content can strengthen the microphase separation behavior in the PDMS- b -PHFBMA diblock copolymers. And the increase in the annealing temperature can also strengthen the microphase separation behavior in the PDMS- b -PHFBMA diblock copolymers. Moreover, Flory-Huggins thermodynamic theory was preliminarily used to explain the microphase separation behavior in the PDMS- b -PHFBMA diblock copolymers. 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009 [source]

    Synthesis and properties of organic/inorganic hybrid nanoparticles prepared using atom transfer radical polymerization

    Tzong-Liu Wang
    Abstract The synthesis of organic/inorganic hybrid materials was conducted by atom transfer radical polymerization (ATRP) of styrene and methyl methacrylate (MMA) from the surface of silica colloids. Colloidal initiators were prepared by the functionalization of silica nanoparticles with (3-(2-bromoisobutyryl)propyl) dimethylethoxysilane (BIDS). Well-defined polymer chains were grown from the nanoparticle surfaces to yield individual particles composed of a silica core and a well-defined outer polystyrene (PS) or poly(methyl methacrylate) (PMMA) layer. Fourier transform infrared (FTIR) and solid state 13C and 29Si-NMR spectroscopy confirmed the successful modification of nanosilica surfaces. Subsequent grafting of polymers on silica surfaces by ATRP was also performed with success based on FTIR and NMR data. Scanning electron microscopy (SEM) and silicon mapping showed both hybrid materials were homogeneous dispersion systems. Energy dispersive X-ray spectrometer (EDS) analysis indicated that the BIDS initiator was covalently attached on surfaces of silica nanoparticles and ATRP of styrene and MMA were accomplished. Thermogravimetric analysis (TGA) results displayed higher thermal stabilities for both nanohybrids in comparison with the linear-type vinyl polymers. Contact angle measurements revealed the nanomaterials character for both silica-based hybrid materials. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    Graft copolymerization of methyl methacrylate with an N -substituted maleimide,liquid-crystalline copolymer by atom transfer radical polymerization

    T. ak
    Abstract The synthesis of novel copolymers consisting of a side-group liquid-crystalline backbone and poly (methyl methacrylate) grafts were realized by the use of atom transfer radical polymerization (ATRP). In the first stage, the bromine-functional copolymers 6-(4-cyanobiphenyl-4,-oxy)hexyl acrylate and (2,5-dioxo-2,5-dihydro-1H -pyrrole-1-yl)methyl 2-bromopropanoate were synthesized by free-radical polymerization. These copolymers were used as initiators in the ATRP of methyl methacrylate to yield graft copolymers. Both the macroinitiator and graft copolymers were characterized by 1H-NMR, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. The ATRP graft copolymerization was supported by an increase in the molecular weight of the graft copolymers compared to that of the macroinitiator and also by their monomodal molecular weight distribution. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]

    The synthesis of poly(3-hydroxybutyrate)- g -poly(methylmethacrylate) brush type graft copolymers by atom transfer radical polymerization method

    Hlya Arslan
    Abstract Brush type of poly (3-hydroxy butyrate), PHB, copolymer synthesis has been reported. Natural PHB was chlorinated by passing chlorine gas through PHB solution in CHCl3/CCl4 mixture (75/25 v/v) to prepare chlorinated PHB, PHB-Cl, with the chlorine contents varying between 2.18 and 39.8 wt %. Toluene solution of PHB-Cl was used in the atom transfer radical polymerization (ATRP) of methyl methacrylate, MMA, in the presence of cuprous bromide (CuBr)/2,2,-bipyridine complex as catalyst, at 90C. This "grafting from" technique led to obtain poly (3-hydroxybutyrate)-g-poly(methylmethacrylate) (PHB- g -PMMA) brush type graft copolymers (cylindrical brush). The polymer brushes were fractionated by fractional precipitation methods and the , values calculated from the ratio of the volume of nonsolvent to volume of solvent of brushes were ranged between 2.8 and 9.5 depending on the molecular weight, grafting density, and side chain length of the brushes, while the , values of PHB, PHB-Cl, and homo-PMMA were 2.7,3.8, 0.3,2.4, and 3.0,3.9, respectively. The fractionated brushes were characterized by gel permeation chromatography, 1H-NMR spectrometry, thermogravimetric analysis (TGA), and differential scanning calorimetry techniques. PHB- g -PMMA brush type graft copolymers showed narrower molecular weight distribution (mostly in range between 1.3 and 2.2) than the PHB-Cl macroinitiator (1.6,3.5). PHB contents in the brushes were calculated from their TGA thermograms and found to be in range between 22 and 42 mol %. The morphologies of PHB- g -PMMA brushes were also studied by scanning electron microscopy. 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source]

    Synthesis of liquid crystalline,amorphous block copolymers by the combination of atom transfer and promoted cationic polymerization

    S. Demirhan
    Abstract Block copolymers of liquid crystalline 6-(4-cyanobiphenyl-4,-oxy) hexyl acrylate (LC6) and cyclohexene oxide (CHO) were obtained by the combination of atom transfer radical polymerization (ATRP) and promoted cationic polymerization (PCP). In the first part, a bifunctional initiator containing benzoin and halide groups in the same structure was used as an initiator in ATRP of LC6, in diphenyl ether in conjunction with CuBr/N,N,N,,N,,N,-pentamethyldiethylenetriamine as a catalyst. The obtained photoactive liquid crystalline polymers poly[6-(4-cyanobiphenyl-4,-oxy)hexyl acrylate] (PLC6), were used to induce polymerization of CHO through formation of electron donor polymeric radicals upon photolysis and subsequent oxidation to corresponding carbocations in the presence of onium salt. The spectral, thermal and optical measurements confirmed a full combination of ATRP and PCP, which resulted in the formation of AB-type block copolymers. 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source]

    Atom transfer radical polymerization and copolymerization of vinyl acetate catalyzed by copper halide/terpyridine

    AICHE JOURNAL, Issue 3 2009
    Huadong Tang
    Abstract Copper-mediated atom transfer radical polymerization (ATRP) is versatile for living polymerizations of a wide range of monomers, but ATRP of vinyl acetate (VAc) remains challenging due to the low homolytic cleavage activity of the carbon-halide bond of the dormant poly(vinyl acetate) (PVAc) chains and the high reactivity of growing PVAc radicals. Therefore, all the reported highly active copper-based catalysts are inactive in ATRP of VAc. Herein, we report the first copper-catalyst mediated ATRP of VAc using CuBr/2,2,:6,,2,-terpyridine (tPy) or CuCl/tPy as catalysts. The polymerization was a first order reaction with respect to the monomer concentration. The molecular weights of the resulting PVAc linearly increased with the VAc conversion. The living character was further proven by self-chain extension of PVAc. Using polystyrene (PS) as a macroinitiator, a well-defined diblock copolymer PS-b-PVAc was prepared. Hydrolysis of the PS-b-PVAc produced a PS-b-poly(vinyl alcohol) amphiphilic diblock copolymer. 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

    Amphiphilic polymer conetworks prepared by controlled radical polymerization using a nitroxide cross-linker

    Weijie Zhao
    Abstract Tandem atom transfer radical polymerization (ATRP) and nitroxide-mediated radical polymerization (NMRP) were used to synthesize a polystyrene- co -poly(acrylic acid) (poly(St- co -AA)) network, in which the two components were interconnected by covalent bond. First, a specific cross-linker, 1,4-bis(1,-(4,-acryloyloxy-2,,2,,6,,6,-tetramethylpiperidinyloxy)ethyl)benzene (di -AET), a bifunctional alkoxyamine possessing two acrylate groups, was copolymerized with tert -butyl acrylate through ATRP to prepare a precursor gel. The gel was then used to initiate the NMRP of styrene to prepare poly(St- co -(t -BA)) conetwork, in which the cross-linkages are composed of polystyrene segments. Finally, the poly(St- co -(t -BA)) conetwork was hydrolyzed to produce amphiphilic poly(St- co -AA) conetwork. The resulting gels show swelling ability in both organic solvent and water, which is characteristic of amphiphilic conetworks. 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4141,4149, 2010 [source]

    Investigation of thiol-ene addition reaction on poly(isoprene) under UV irradiation: Synthesis of graft copolymers with "V"-shaped side chains

    Guowei Wang
    Abstract Poly(isoprene) (PI) with pendant functional groups was successfully synthesized by thiol-ene addition reaction under 365 nm UV irradiation, and the functionalized PI was further modified and used to prepare graft copolymers with "V"-shaped side chains. First, the pendant SCH2CH(OH)CH2OH groups were introduced to PI by thiol-ene addition reaction between 1-thioglycerol and double bonds, and the results showed that the addition reaction carried out only on double bonds of 1,2-addition isoprene units. After the esterification of hydroxyl groups by 2-bromoisobutyryl bromide, the forming macroinitiator was used to initiate the atom transfer radical polymerization (ATRP) of styrene (St) and tert -butyl acrylate (tBA), and the graft copolymers PI- g -PS2 and PI- g -PtBA2 or PI- g -PAA2 (by hydrolysis of PI- g -PtBA2) were obtained, respectively. It was confirmed that the graft density of side chains on PI main chains could be easily controlled by variation of the contents of modified 1,2-addition isoprene units on PI. 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3797,3806, 2010 [source]

    Synthesis and self-assembly of well-defined cyclodextrin-centered amphiphilic A14B7 multimiktoarm star copolymers based on poly(,-caprolactone) and poly(acrylic acid)

    Peng-Fei Gou
    Abstract Novel amphiphilic A14B7 multimiktoarm star copolymers composed of 14 poly(,-caprolactone) (PCL) arms and 7 poly(acrylic acid) (PAA) arms with ,-cyclodextrin (,-CD) as core moiety were synthesized by the combination of controlled ring-opening polymerization (CROP) and atom transfer radical polymerization (ATRP). 14-Arm star PCL homopolymers (CDSi-SPCL) were first synthesized by the CROP of CL using per-6-(tert -butyldimethylsilyl)-,-CD as the multifunctional initiator in the presence of Sn(Oct)2 at 125 C. Subsequently, the hydroxyl end groups of CDSi-SPCL were blocked by acetyl chloride. After desilylation of the tert -butyldimethylsilyl ether groups from the ,-CD core, 7 ATRP initiating sites were introduced by treating with 2-bromoisobutyryl bromide, which further initiated ATRP of tert -butyl acrylate (tBA) to prepare well-defined A14B7 multimiktoarm star copolymers [CDS(PCL-PtBA)]. Their molecular structures and physical properties were in detail characterized by 1H NMR, SEC-MALLS, and DSC. The selective hydrolysis of tert -butyl ester groups of the PtBA block gave the amphiphilic A14B7 multimiktoarm star copolymers [CDS(PCL-PAA)]. These amphiphilic copolymers could self-assemble into multimorphological aggregates in aqueous solution, which were characterized by dynamic light scattering (DLS), transmission electron microscopy (TEM) and atomic force microscopy (AFM). 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2961,2974, 2010 [source]

    Water-soluble triply-responsive homopolymers of N,N -dimethylaminoethyl methacrylate with a terminal azobenzene moiety

    Xinde Tang
    Abstract Novel water-soluble triply-responsive homopolymers of N,N -dimethylaminoethyl methacrylate (DMAEMA) containing an azobenzene moiety as the terminal group were synthesized by atom transfer radical polymerization (ATRP) technique. The ATRP process of DMAEMA was initiated by an azobenzene derivative substituted with a 2-bromoisobutyryl group (Azo-Br) in the presence of CuCl/Me6TREN in 1,4-dioxane as a catalyst system. The molecular weights and their polydispersities of the resulting homopolymers (Azo-PDMAEMA) were characterized by gel permeation chromatography (GPC). The homopolymers are soluble in aqueous solution and exhibit a lower critical solution temperature (LCST) that alternated reversibly in response to Ph and photoisomerization of the terminal azobenzene moiety. It was found that the LCST increased as pH decreased in the range of testing. Under UV light irradiation, the trans -to- cis photoisomerization of the azobenzene moiety resulted in a higher LCST, whereas it recovered under visible light irradiation. This kind of polymers should be particularly interesting for a variety of potential applications in some promising areas, such as drug controlled-releasing carriers and intelligent materials because of the multistimuli responsive property. 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2564,2570, 2010 [source]

    Synthesis of well-defined rod-coil block copolymers containing trifluoromethylated poly(phenylene oxide)s by chain-growth condensation polymerization and atom transfer radical polymerization

    Yun Jun Kim
    Abstract Well-defined trifluoromethylated poly(phenylene oxide)s were synthesized via nucleophilic aromatic substitution (SNAr) reaction by a chain-growth polymerization manner. Polymerization of potassium 4-fluoro-3-(trifluoromethyl)phenolate in the presence of an appropriate initiator yielded polymers with molecular weights of ,4000 and polydispersity indices of <1.2, which were characterized by 1H nuclear magnetic resonance spectroscopy and gel permeation chromatography. Initiating sites for atom transfer radical polymerization (ATRP) were introduced at the either side of chain ends of the poly(phenylene oxide), and used for ATRP of styrene and methyl methacrylate, yielding well-defined rod-coil block copolymers. Differential scanning calorimetry study indicated that the well-defined trifluoromethylated poly(phenylene oxide)s showed high crystallinity and were immiscible with polystyrene. 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1049,1057, 2010 [source]

    Titanium-mediated [CpTiCl2(OEt)] ring-opening polymerization of lactides: A novel route to well-defined polylactide-based complex macromolecular architectures

    Nikolaos Petzetakis
    Abstract Among three cyclopentadienyl titanium complexes studied, CpTiCl2(OEt), containing a 5% excess CpTiCl3, has proven to be a very efficient catalyst for the ring-opening polymerization (ROP) of L -lactide (LLA) in toluene at 130 C. Kinetic studies revealed that the polymerization yield (up to 100%) and the molecular weight increase linearly with time, leading to well-defined PLLA with narrow molecular weight distributions (Mw/Mn , 1.1). Based on the above results, PS- b -PLLA, PI- b -PLLA, PEO- b -PLLA block copolymers, and a PS- b -PI- b -PLLA triblock terpolymer were synthesized. The synthetic strategy involved: (a) the preparation of OH-end-functionalized homopolymers or diblock copolymers by anionic polymerization, (b) the reaction of the OH-functionalized polymers with CpTiCl3 to give the corresponding Ti-macrocatalyst, and (c) the ROP of LLA to afford the final block copolymers. PMMA- g -PLLA [PMMA: poly(methyl methacrylate)] was also synthesized by: (a) the reaction of CpTiCl3 with 2-hydroxy ethyl methacrylate, HEMA, to give the Ti-HEMA-catalyst, (b) the ROP of LLA to afford a PLLA methacrylic-macromonomer, and (c) the copolymerization (conventional and ATRP) of the macromonomer with MMA to afford the final graft copolymer. Intermediate and final products were characterized by NMR spectroscopy and size exclusion chromatography, equipped with refractive index and two-angle laser light scattering detectors. 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1092,1103, 2010 [source]

    Biocomplementary interaction behavior in DNA-like and RNA-like polymers

    Chih-Chia Cheng
    Abstract A series of nucleobased polymers and copolymers were synthesized through atom transfer radical polymerization (ATRP). Biocomplementary DNA- and RNA-like supramolecular complexes are formed in dilute DMSO solution through nucleobase recognition. 1H NMR titration studies of these complexes in CDCl3 indicated that thymine-adenine (T-A) and uracil-adenine (U-A) complexes form rapidly on the NMR time scale with high association constants (up to 534 and 671 M,1, respectively) and result in significant Tg increase. WAXD and differential scanning calorimetry analyzes in the bulk state indicate the presence of highly physical cross-linked structures and provide further details into the nature of the self-assembly of these systems. Furthermore, this study is of discussion on the difference in the hydrogen bond strength between T-A and U-A base pairs within polymer systems, indicating that the strength of hydrogen bonds in RNA U-A pairs is stronger than that in DNA T-A base pairs. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6388,6395, 2009 [source]

    Synthesis of amphiphilic and thermoresponsive ABC miktoarm star terpolymer via a combination of consecutive click reactions and atom transfer radical polymerization

    Changhua Li
    Abstract Well-defined amphiphilic and thermoresponsive ABC miktoarm star terpolymer consisting of poly(ethylene glycol), poly(tert -butyl methacrylate), and poly(N -isopropylacrylamide) arms, PEG(- b -PtBMA)- b -PNIPAM, was synthesized via a combination of consecutive click reactions and atom transfer radical polymerization (ATRP). Click reaction of monoalkynyl-terminated PEG with a trifunctional core molecule bis(2-azidoethyl)amine, (N3)2NH, afforded difunctional PEG possessing an azido and a secondary amine moiety at the chain end, PEG- NHN3. Next, the amidation of PEG- NHN3 with 2-chloropropionyl chloride led to PEG-based ATRP macroinitiator, PEG(N3)Cl. The subsequent ATRP of N -isopropylacrylamide (NIPAM) using PEG(N3)Cl as the macroinitiator led to PEG(N3)- b -PNIPAM bearing an azido moiety at the diblock junction point. Finally, well-defined ABC miktoarm star terpolymer, PEG(- b -PtBMA)- b -PNIPAM, was prepared via the click reaction of PEG(N3)- b -PNIPAM with monoalkynyl-terminated PtBMA. In aqueous solution, the obtained ABC miktoarm star terpolymer self-assembles into micelles consisting of PtBMA cores and hybrid PEG/PNIPAM coronas, which are characterized by dynamic and static laser light scattering, and transmission electron microscopy. On heating above the phase transition temperature of PNIPAM in the hybrid corona, micelles initially formed at lower temperatures undergo further structural rearrangement and fuse into much larger aggregates solely stabilized by PEG coronas. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4001,4013, 2009 [source]

    Controlled/living heterogeneous radical polymerization in supercritical carbon dioxide

    Per B. Zetterlund
    Abstract Supercritical carbon dioxide (scCO2) is an inexpensive and environmentally friendly medium for radical polymerizations. ScCO2 is suited for heterogeneous controlled/living radical polymerizations (CLRPs), since the monomer, initiator, and control reagents (nitroxide, etc.) are soluble, but the polymer formed is insoluble beyond a critical degree of polymerization (Jcrit). The precipitated polymer can continue growing in (only) the particle phase giving living polymer of controlled well-defined microstructure. The addition of a colloidal stabilizer gives a dispersion polymerization with well-defined colloidal particles being formed. In recent years, nitroxide-mediated polymerization (NMP), atom transfer radical polymerization (ATRP), and reversible addition fragmentation chain transfer (RAFT) polymerization have all been conducted as heterogeneous polymerizations in scCO2. This Highlight reviews this recent body of work, and describes the unique characteristics of scCO2 that allows composite particle formation of unique morphology to be achieved. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3711,3728, 2009 [source]

    Preparation of molecularly imprinted polymer microspheres via atom transfer radical precipitation polymerization

    Baiyi Zu
    Abstract The first combined use of atom transfer radical polymerization (ATRP) and precipitation polymerization in the molecular imprinting field is described. The utilized polymerization technique, namely atom transfer radical precipitation polymerization (ATRPP), provides MIP microspheres with obvious molecular imprinting effects towards the template, fast template binding kinetics and an appreciable selectivity over structurally related compounds. The living chain propagation mechanism in ATRPP results in MIP spherical particles with diameters (number-average diameter Dn , 3 ,m) much larger than those prepared via traditional radical precipitation polymerization (TRPP). In addition, the MIP microspheres prepared via ATRPP have also proven to show significantly higher high-affinity binding site densities on their surfaces than the MIP generated via TRPP, while the binding association constants Ka and apparent maximum numbers Nmax of the high-affinity sites as well as the specific template bindings are almost the same in the two cases. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3257,3270, 2009 [source]

    Synthesis of stimuli-responsive macroazoinitiators and their use as an inistab toward hairy polymer latex particles

    Syuji Fujii
    Abstract Stimuli-responsive macroazoinitiators with central azo unit have been synthesized by atom transfer radical polymerization (ATRP) of 2-(dimethylamino)ethyl methacrylate or 2-(diethylamino)ethyl methacrylate in 2-propanol at 25 C. The mean degree of polymerization of the polymer chains besides the azo group was fixed between 25 and 60. 1H NMR, gel permeation chromatography, UV-Vis spectrophotometer, and surface tensiometer were used to characterize the stimuli-responsive macroazoinitiators in terms of their chemical structure, molecular weight, polydispersity, and pH-responsive behavior, respectively. Eventually, dispersion polymerization of styrene using the poly[2-(diethylamino)ethyl methacrylate] (PDEA) macroazoinitiator as an inistab (initiator + stabilizer) in 2-propanol medium was conducted. Near-monodisperse 98 nm polystyrene (PS) latex particles with pH-responsive PDEA hair were successfully synthesized. The PS latex particles with the PDEA hair can be dispersed in acidic aqueous media where the PDEA hair was protonated and was solvated, and can be flocculated in basic aqueous media where the PDEA hair was deprotonated and was precipitated. This dispersion-flocculation cycle was reversible. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3431,3443, 2009 [source]