Macroinitiator

Distribution by Scientific Domains
Distribution within Polymers and Materials Science


Selected Abstracts


Surface Polymerization of Hydrophilic Methacrylates from Ultrafine Silica Sols in Protic Media at Ambient Temperature: A Novel Approach to Surface Functionalization Using a Polyelectrolytic Macroinitiator,

ADVANCED MATERIALS, Issue 18 2003
X. Chen
A convenient one-pot synthesis of polymer-grafted nano-sized silica particles using atom transfer radical polymerization (see Figure) is described. Physical adsorption of a cationic macroinitiator allows polymerization of a range of hydrophilic methacrylates. A high degree of coverage of the silica sol particles by the grafted polymer chains was indicated. [source]


Synthesis and characterization of temperature-sensitive block copolymers from poly(N -isopropylacrylamide) and 4-methyl-,-caprolactone or 4-phenyl-,-caprolactone

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2010
Ren-Shen Lee
Abstract This study synthesizes thermally sensitive block copolymers poly(N -isopropylacrylamide)- b -poly(4-methyl-,-caprolactone) (PNIPA- b -PMCL) and poly(N -isopropylacrylamide)- b -poly(4-phenyl-,-caprolactone) (PNIPA- b -PBCL) by ring-opening polymerization of 4-methyl-,-caprolactone (MCL) or 4-phenyl-,-caprolactone (BCL) initiated from hydroxy-terminated poly(N -isopropylacrylamide) (PNIPA) as the macroinitiator in the presence of SnOct2 as the catalyst. This research prepares a PNIPA bearing a single terminal hydroxyl group by telomerization using 2-hydroxyethanethiol (ME) as a chain-transfer agent. These copolymers are characterized by differential scanning calorimetry (DSC), 1H-NMR, FTIR, and gel permeation chromatography (GPC). The thermal properties (Tg) of diblock copolymers depend on polymer compositions. Incorporating larger amount of MCL or BCL into the macromolecular backbone decreases Tg. Their solutions show transparent below a lower critical solution temperature (LCST) and opaque above the LCST. LCST values for the PNIPA- b -PMCL aqueous solution were observed to shift to lower temperature than that for PNIPA homopolymers. This work investigates their micellar characteristics in the aqueous phase by fluorescence spectroscopy, transmission electron microscopy (TEM), and dynamic light scattering (DLS). The block copolymers formed micelles in the aqueous phase with critical micelle concentrations (CMCs) in the range of 0.29,2.74 mg L,1, depending on polymer compositions, which dramatically affect micelle shape. Drug entrapment efficiency and drug loading content of micelles depend on block polymer compositions. 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]


Morphology and photophysical properties of a thermally responsive fluorescent material based on a rod-coil tri-block copolymer

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008
Zhun Ma
Abstract A thermally responsive rod-coil poly[poly (N -isopropylacrylamide)- b -polyfluorene- b -poly(N -isopropylacrylamide)] triblock copolymer has been successfully synthesized by atom transfer radical polymerization from an end-functionalized macroinitiator. The thermochromic behavior and relevant morphology of this polymer were investigated by UV-vis spectra, DLS, and AFM, respectively, at various temperatures. A thermally responsive fluorescent material was achieved facilely by combining the optically active polyfluorene with temperature-responsive poly(N -isopropylacrylamide). All the measurements demonstrated that in the region of 25,45C, the polymer underwent a phase transition and the corresponding change in optical properties in its water solution. However, the polymer did not show completely reversible behavior upon heating and cooling. On the basis of the comparison with two other thermally responsive conjugated polymers in literatures, a tentative mechanism has been proposed that ,,, interaction induced rigid segments to remain chain conformation and packing styles as in collapsed state. 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source]


Preparation and applicability of functionalized polyethylene with an ethylene/1,7-octadiene copolymer

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008
Eun-Soo ParkArticle first published online: 3 JUN 200
Abstract The copolymerization of ethylene and 1,7-octadiene was carried out to synthesize polyethylene with unreacted vinyl groups. The prepared copolymer [poly (ethylene- co -1,7-octadiene) (PEOD)] was epoxidized with peracetic acid, m -chloroperbenzoic acid, or formic acid/H2O2. Of these, peracetic acid gave the best results. Epoxidized PEOD was subjected to a reaction with 2-mercaptobenzimidazole and poly(L -lactic acid). The bromination of PEOD was also performed in the presence of a Br2/HBr solution at room temperature. The brominated poly(ethylene- co -1,7-octadiene) (PEOD-Br) was used as a macroinitiator for atom transfer radical polymerization. The polymerization of styrene, butyl methacrylate, and glycidyl methacrylate was performed in bulk or solution at 120C with a PEOD-Br/CuBr/2,2,-dipyridyl initiator system. The thermal properties of the graft copolymers and the efficiency of the graft polymerization were investigated. These graft copolymers have potential applications as interfacial modifiers. 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

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2008
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

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007
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]


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]


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

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2010
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 of high glass transition temperature copolymers based on poly(vinyl chloride) via single electron transfer,Degenerative chain transfer mediated living radical polymerization (SET-DTLRP) of vinyl chloride in water

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 24 2009
Jorge F. J. Coelho
Abstract ,,,-di(iodo) poly(isobornyl acrylate) macroiniators (,,,-di(iodo)PIA) with number average molecular weight from Mn,TriSEC = 11,456 to Mn,TriSEC = 94,361 were synthesized by single electron transfer-degenerative chain transfer mediated living radical polymerization (SET-DTLRP) of isobornyl acrylate (IA) initiated with iodoform (CHI3) and catalyzed by sodium dithionite (Na2S2O4) in water at 35 C. The plots of number average molecular weight vs conversion and ln{[M]0/[M]} vs time are linear, indicating a controlled polymerization. ,,,-di(iodo) poly(isobornyl acrylate) have been used as a macroinitiator for the SET-DTLRP of vinyl chloride (VCM) leading to high Tg block copolymers PVC-b-PIA-b-PVC. The dynamic mechanical thermal analysis of the block copolymers suggests just one phase indicating that copolymer behaves as a single material. This technology provides the possibility of synthesizing materials based on PVC with higher Tg in aqueous medium. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009 [source]


Synthesis of biocompatible and biodegradable block copolymers of polyvinyl alcohol- block -poly(,-caprolactone) using metal-free living cationic polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2009
Izabela Magdalena Zaleska
Abstract Applications of metal-free living cationic polymerization of vinyl ethers using HClEt2O are reported. Product of poly(vinyl ether)s possessing functional end groups such as hydroxyethyl groups with predicted molecular weights was used as a macroinitiator in activated monomer cationic polymerization of ,-caprolactone (CL) with HClEt2O as a ring-opening polymerization. This combination method is a metal-free polymerization using HClEt2O. The formation of poly(isobutyl vinyl ether)- b -poly(,-caprolactone) (PIBVE- b -PCL) and poly(tert -butyl vinyl ether)- b -poly(,-caprolactone) (PTBVE- b -PCL) from two vinyl ethers and CL was successful. Therefore, we synthesized novel amphiphilic, biocompatible, and biodegradable block copolymers comprised polyvinyl alcohol and PCL, namely PVA- b -PCL by transformation of acid hydrolysis of tert -butoxy moiety of PTBVE in PTBVE- b -PCL. The synthesized copolymers showed well-defined structure and narrow molecular weight distribution. The structure of resulting block copolymers was confirmed by 1H NMR, size exclusion chromatography, and differential scanning calorimetry. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5169,5179, 2009 [source]


Synthesis of PMMA- b -PBA block copolymer in homogeneous and miniemulsion systems by DPE controlled radical polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2009
Ying-Da Luo
Abstract In this research, poly(methyl methacrylate)- b -poly(butyl acrylate) (PMMA- b -PBA) block copolymers were prepared by 1,1-diphenylethene (DPE) controlled radical polymerization in homogeneous and miniemulsion systems. First, monomer methyl methacrylate (MMA), initiator 2,2,-azobisisobutyronitrile (AIBN) and a control agent DPE were bulk polymerized to form the DPE-containing PMMA macroinitiator. Then the DPE-containing PMMA was heated in the presence of a second monomer BA, the block copolymer was synthesized successfully. The effects of solvent and polymerization methods (homogeneous polymerization or miniemulsion polymerization) on the reaction rate, controlled living character, molecular weight (Mn) and molecular weight distribution (PDI) of polymers throughout the polymerization were studied and discussed. The results showed that, increasing the amounts of solvent reduced the reaction rate and viscosity of the polymerization system. It allowed more activation,deactivation cycles to occur at a given conversion thus better controlled living character and narrower molecular weight distribution of polymers were demonstrated throughout the polymerization. Furthermore, the polymerization carried out in miniemulsion system exhibited higher reaction rate and better controlled living character than those in homogeneous system. It was attributed to the compartmentalization of growing radicals and the enhanced deactivation reaction of DPE controlled radical polymerization in miniemulsified droplets. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4435,4445, 2009 [source]


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

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2009
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]


Preparation of monodisperse nanoparticles containing poly(propylene imine)(NH2)32 -polystyrene

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 11 2009
Hu Liu
Abstract Polypropylenimine dendrimer (DAB-Am-32, generation 4.0) was converted into a macroinitiator DAB-Am-32-Cl via reaction with 2-chloropropionyl chloride. Monodisperse nanoparticles containing poly(propylene imine)(NH2)32 -polystyrene were prepared by emulsion atom transfer radical polymerization (ATRP) of styrene (St), using the DAB-Am-32-Cl/CuCl/bpy as initiating system. The structure of macroinitiator was characterized by FTIR spectrum, 1H NMR, and 13C NMR. The structure of poly(propylene imine)(NH2)32 -polystyrene was characterized by FT-IR spectrum and 1H NMR; the molecular weight and molecular weight distribution of poly(propylene imine)(NH2)32 -polystyrene were characterized by gel permeation chromatograph (GPC). The morphology, size and size distribution of the nanoparticles were characterized by photon correlation spectroscopy (PCS), transmission electron microscopy (TEM), and atomic force microscopy (AFM). The effects of monomer/macroinitiator ratio and surfactant concentration on the size and size distribution of the nanoparticles were investigated. It was found that the diameters of the nanoparticles were smaller than 100 nm (30,80 nm) and monodisperse; moreover, the particle size could be controlled by monomer/macroinitiator ratios and surfactant concentration. With the increasing of the ratio of St/DAB-Am-32-Cl, the number-average diameter (Dn), weight-average diameter (Dw) were both increased gradually. With enhancing the surfactant concentration, the measured Dh of the nanoparticles decreased, while the polydispersity increased. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2892,2904, 2009 [source]


Degradable star polymers with high "click" functionality

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2009
James T. Wiltshire
Abstract Degradable polyester-based star polymers with a high level of functionality in the arms were synthesized via the "arms first" approach using an acetylene-functional block copolymer macroinitiator. This was achieved by using 2-hydroxyethyl 2,-methyl-2,-bromopropionate to initiate the ring-opening polymerization (ROP) of caprolactone monomer followed by an atom transfer radical polymerization (ATRP) of a protected acetylene monomer, (trimethylsilyl)propargyl methacrylate. The hydroxyl end-group of the resulting block copolymer macroinitiator was subsequently crosslinked under ROP conditions using a bislactone monomer, 4,4,-bioxepanyl-7,7,-dione, to generate a degradable core crosslinked star (CCS) polymer with protected acetylene groups in the corona. The trimethylsilyl-protecting groups were removed to generate a CCS polymer with an average of 1850 pendent acetylene groups located in the outer block segment of the arms. The increased functionality of this CCS polymer was demonstrated by attaching azide-functionalized linear polystyrene via a copper (I)-catalyzed cycloaddition reaction between the azide and acetylene groups. This resulted in a CCS polymer with "brush-like" arm structures, the grafted segment of which could be liberated via hydrolysis of the polyester star structure to generate molecular brushes. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1485,1498, 2009 [source]


Synthesis of hollow crosslinked miktoarm polymer using miniemulsion as templates

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2009
De'an Xiong
Abstract Hollow crosslinked polymers (HCPs) were synthesized using arm first method via atom transfer radical polymerization. The polymerization process was performed in miniemulsion system, in which the macroinitiator, PEG-Br, was in the water phase, whereas the vinyl-monomer, 4-vinylpyridine (4VP), and the crosslinker, DVB, were in the butanone phase. TEM images and light scattering characterization showed that the resultant polymer contained a hollow space, and the volume of the hollow space could be adjusted by changing the ratio of water to butanone. Also, hollow crosslinked Miktoarm polymers (HCMPs) were synthesized through this method when two different macroinitiators, PEG-Br and PNIPAM-Br, were used to coinitiate the polymerization of the vinyl-monomer, 4VP and DVB. The 1H NMR spectra showed that the hollow polymers contained both PEG arms and PNIPAM arms. The hollow morphologies of the resultant Miktoarm polymers were the same as the HCPs. 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1651,1660, 2009 [source]


Preparation of H-shaped ABCAB terpolymers by atom transfer radical coupling

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2009
Xiaolan Luo
Abstract H-shaped ABCAB terpolymers composed of polystyrene (PS) (A), poly(ethylene oxide) (PEO) (B), and poly(tert -butyl acrylate) (PtBA) (C) were prepared by atom transfer radical coupling reaction using ABC star terpolymers as precursors, CuBr and N,N,N,,N,,N,-pentamethyldiethylenetriamine (PMDETA) as catalysts, and nanosize copper as the reducing agent. The synthesis of 3-miktoarm star terpolymer PS-PEO-(PtBA-Br) involved following steps: (1) the preparation of PS with an active and an ethoxyethyl-ptotected hydroxyl group at the same end; (2) the preparation of diblock copolymer PS- b -PEO with ethoxyethyl-protected group at the junction point through the ring-opening polymerization (ROP) of EO; (3) after de-protection of ethoxyethyl group and further modification of hydroxyl group, tBA was polymerized by atom transfer radical polymerization using PS- b -PEO with 2-bromoisobutyryl functional group as macroinitiator. The H-shaped terpolymer could be successfully formed by atom transfer radical coupling reaction in the presence of small quantity of styrene, CuBr/PMDETA, and Cu at 90 C. The copolymers were characterized by SEC, 1H NMR, and FTIR in detail. The optimized coupling temperature is 90 C. 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 59,68, 2009 [source]


Reverse ATRP process of acrylonitrile in the presence of ionic liquids

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2008
Chen Hou
Abstract An ionic liquid, 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim] [BF4]), was first used as the solvent in azobisisobutyronitrile (AIBN)-initiated reverse atom transfer radical polymerization (RATRP) of acrylonitrile with FeCl3/succinic acid (SA) as the catalyst system. The polymerization in [C4mim][BF4] proceeded in a well-controlled manner as evidenced by kinetic studies. Compared with the polymerization in bulk, the polymerization in [C4mim][BF4] not only showed the best control of molecular weight and its distribution but also provided rather rapid reaction rate with the ratio of [C4mim][BF4] at 200:1:2:4. The polymerization apparent activation energies in [C4mim][BF4] and bulk were calculated to be 48.2 and 55.7 kJ mol,1, respectively. Polyacrylonitrile obtained was successfully used as a macroinitiator to proceed the chain extension polymerization in [C4mim][BF4] via a conventional ATRP process. [C4mim][BF4] and the catalyst system could be easily recycled and reused after simple purification and had no effect on the living nature of polymerization. 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2701,2707, 2008 [source]


Block copolymer preparation by atom transfer radical polymerization under emulsion conditions using a nanoprecipitation technique

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 2 2008
Delphine Chan-Seng
Abstract Living-radical polymerization of acrylates were performed under emulsion atom transfer radical polymerization (ATRP) conditions using latexes prepared by a nanoprecipitation technique previously employed and optimized for the polymerization of styrene. A macroinitiator of poly(n -butyl acrylate) prepared under bulk ATRP was dissolved in acetone and precipitated in an aqueous solution of Brij 98 to preform latex particles, which were then swollen with monomer and heated. Various monomers (i.e. n -butyl acrylate, styrene, and tert -butyl acrylate) were used to swell the particles to prepare homo- and block copolymers from the poly(n -butyl acrylate) macroinitiator. Under these conditions latexes with a relatively good colloidal stability were obtained. Furthermore, amphiphilic block copolymers were prepared by hydrolysis of the tert -butyl groups and the resulting block copolymers were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The bulk morphologies of the polystyrene- b -poly(n -butyl acrylate) and poly(n -butyl acrylate)- b -poly(acrylic acid) copolymers were investigated by atomic force microscopy (AFM) and small angle X-ray scattering (SAXS). 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 625,635, 2008 [source]


Synthesis and characterization of amphiphilic block copolymers with allyl side-groups

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2007
Xiuli Hu
Abstract The synthesis of a new cyclic carbonate monomer containing an allyl group was reported and its biodegradable amphiphilic block copolymer, poly(ethylene glycol)- block -poly(L -lactide- co -5-methyl-5-allyloxycarbonyl-propylene carbonate) [PEG- b -P(LA- co -MAC)] was synthesized by ring-opening polymerization (ROP) of L -lactide (LA) and 5-methyl-5-allyloxycarbonyl-1,3-dioxan-2-one (MAC) in the presence of poly (ethylene glycol) as a macroinitiator, with diethyl zinc as a catalyst. 13C NMR and 1H NMR were used for microstructure identification of the copolymers. The copolymer could form micelles in aqueous solution. The core of the micelles is built of the hydrophobic P(LA- co -MAC) chains, whereas the shell is set up by the hydrophilic PEG blocks. The micelles exhibited a homogeneous spherical morphology and unimodal size distribution. By using the cyclic carbonate monomer containing allyl side-groups, crosslinking of the PEG- b -P(LA- co -MAC) inner core was possible. The adhesion and spreading of ECV-304 cells on the copolymer were better than that on PLA films. Therefore, this biodegradable amphiphilic block copolymer is expected to be used as a biomaterial for drug delivery and tissue engineering. 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5518,5528, 2007 [source]


Novel synthesis of rod-coil block copolymers by combination of coordination polymerization and ATRP

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2007
Koji Ishizu
Abstract Combination of coordination polymerization and atom transfer radical polymerization (ATRP) was applied to a novel synthesis of rod-coil block copolymers. The procedure included the following steps: (1) monoesterification reaction of ethylene glycol with 2-bromoisobutyryl bromide yielded a ,-bromo, ,-hydroxy bifunctional initiator, (2) CpTiCl3 (bifunctional initiator) catalyst was prepared from a mixture of trichlorocyclopentadienyl titanium (CpTiCl3) and bifunctional initiator. Coordination polymerization of n- butyl isocyanate initiated by such catalyst provided a well-defined macroinitiator, poly(n- butyl isocyanate)-Br (PBIC-Br), and (3) ATRP method of vinyl monomers using PBIC-Br provided rod (PBIC)-coil block copolymers. 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4037,4042, 2007 [source]


Synthesis and characterization of multiblock copolymers composed of poly(5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one) outer blocks and poly(L -lactide) inner blocks

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2006
Jamie M. Messman
Abstract Ethylene glycol (EG) initiated, hydroxyl-telechelic poly(L -lactide) (PLLA) was employed as a macroinitiator in the presence of a stannous octoate catalyst in the ring-opening polymerization of 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MBC) with the goal of creating A,B,A-type block copolymers having polycarbonate outer blocks and a polyester center block. Because of transesterification reactions involving the PLLA block, multiblock copolymers of the A,(B,A)n,B,A type were actually obtained, where A is poly(5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one), B is PLLA, and n is greater than 0. 1H and 13C NMR spectroscopy of the product copolymers yielded evidence of the multiblock structure and provided the lactide sequence length. For a PLLA macroinitiator with a number-average molecular weight of 2500 g/mol, the product block copolymer had an n value of 0.8 and an average lactide sequence length (consecutive C6H8O4 units uninterrupted by either an EG or MBC unit) of 6.1. For a PLLA macroinitiator with a number-average molecular weight of 14,400 g/mol, n was 18, and the average lactide sequence length was 5.0. Additional evidence of the block copolymer architecture was revealed through the retention of PLLA crystallinity as measured by differential scanning calorimetry and wide-angle X-ray diffraction. Multiblock copolymers with PLLA crystallinity could be achieved only with isolated PLLA macroinitiators; sequential addition of MBC to high-conversion L -lactide polymerizations resulted in excessive randomization, presumably because of residual L -lactide monomer. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6817,6835, 2006 [source]


Synthesis of diblock copolymers by combining stable free radical polymerization and atom transfer radical polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2006
Yan Shi
Abstract A stable nitroxyl radical functionalized with an initiating group for atom transfer radical polymerization (ATRP), 4-(2-bromo-2-methylpropionyloxy)-2,2,6,6-tetramethyl-1-piperidinyloxy (Br-TEMPO), was synthesized by the reaction of 4-hydroxyl-2,2,6,6-tetramethyl-1-piperidinyloxy with 2-bromo-2-methylpropionyl bromide. Stable free radical polymerization of styrene was then carried out using a conventional thermal initiator, dibenzoyl peroxide, along with Br-TEMPO. The obtained polystyrene had an active bromine atom for ATRP at the ,-end of the chain and was used as the macroinitiator for ATRP of methyl acrylate and ethyl acrylate to prepare block copolymers. The molecular weights of the resulting block copolymers at different monomer conversions shifted to higher molecular weights and increased with monomer conversion. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2468,2475, 2006 [source]


Synthesis of comb-like polystyrene with poly(N -phenyl maleimide- alt-p -chloromethyl styrene) as macroinitiator

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2006
Yan Shi
Abstract The copolymerization of N -phenyl maleimide and p -chloromethyl styrene via reversible addition,fragmentation chain transfer (RAFT) process with AIBN as initiator and 2-(ethoxycarbonyl)prop-2-yl dithiobenzoate as RAFT agent produced copolymers with alternating structure, controlled molecular weights, and narrow molecular weight distributions. Using poly(N -phenyl maleimide- alt - p -chloromethyl styrene) as the macroinitiator for atom transfer radical polymerization of styrene in the presence of CuCl/2,2,-bipyridine, well-defined comb-like polymers with one graft chain for every two monomer units of backbone polymer were obtained. 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2069,2075, 2006 [source]


Organosoluble star polymers from a cyclodextrin core

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2005
Khaled Karaky
Abstract Well-defined star polymers were synthesized with a combination of the core-first method and atom transfer radical polymerization. The control of the architecture of the macroinitiator based on ,-cyclodextrin bearing functional bromide groups was determined by 13C NMR, fast atom bombardment mass spectrometry, and elemental analysis. In a second step, the polymerization of the tert -butyl acrylate monomer was optimized to avoid a star,star coupling reaction and allowed the synthesis of a well-defined organosoluble polymer star. The determination of the macromolecular dimensions of these new star polymers by size exclusion chromatography/light scattering was in agreement with the structure of armed star polymers in a large range of predicted molecular weights. This article describes a new approach to polyelectrolyte star polymers by postmodification of poly(tert -butyl acrylate) by acrylic arm hydrolysis in a water-soluble system. 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5186,5194, 2005 [source]


Synthesis of well-defined AB20 -type star polymers with cyclodextrin-core by combination of NMP and ATRP

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2005
Yutaka Miura
Abstract The synthesis of an AB20 -type heteroarm star polymer consisting of a polystyrene arm and 20-arms of poly(methyl methacrylate) or poly(tert -butyl acrylate) was carried out using the combination of nitroxide-mediated polymerization (NMP) and atom transfer radical polymerization (ATRP). The NMP of styrene was carried out using mono-6-[4-(1,-(2,,2,,6,,6,-tetramethyl-1,-piperidinyloxy)-ethyl)benzamido]-,-cyclodextrin peracetate (1) to afford end-functionalized polystyrene with an acetylated ,-cyclodextrin (,-CyD) unit (prepolymer 2) with a number-average molecular weight (Mn) of 11700 and a polydispersity (Mw/Mn) of 1.17. After deacetylation of prepolymer 2, the resulting polymer was reacted with 2-bromoisobutyric anhydride to give end-functionalized polystyrene with 20(2-bromoisobutyrol)s ,-CyD, macroinitiator 4. The copper (I)-mediated ATRP of methyl methacrylate (MMA) and tert -butyl acrylate (tBA) was carried out using macroinitiator 4. The resulting polymers were isolated by SEC fractionation to produce AB20 -type star polymers with a ,-CyD-core, 5. The well-defined structure of 5 with weight-average molecular weight (Mw)s of 13,500,65,300 and Mw/Mn's of 1.26,1.28 was demonstrated by SEC and light scattering measurements. The arm polymers were separated from 5 by destruction with 28 wt % sodium methoxide in order to analyze the details of their characteristic structure. 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4271,4279, 2005 [source]


Nitroxide-mediated homo- and block copolymerization of styrene and multifunctional acryl- and methacryl derivatives

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2005
Meizhen Yin
Abstract The ability of different alkoxyamines (I1, I2, I3, I4, and I5) to initiate controlled radical polymerization of styrene was evaluated. Among them, 2-hydroxymethyl-2-[(2-methyl-1-phenyl-propyl)-(1-phenyl-ethoxy)-amino]-propane-1,3-diol (I5) gave the highest polymerization rate of styrene, and the best control over the molecular weight and the molecular weight distribution of polystyrene. Kinetic studies confirmed that with initiator I5 the polymerization of styrene proceeded in a controlled way. The controlled radical homopolymerization of multifunctional acryl- and methacryl derivatives using initiator I5 could not be realized as demonstrated by the high polydispersities (PD) obtained. However, it was possible to polymerize multifunctional acryl- and methacryl derivatives using a polystyrene macroinitiator (Pst) and, thus, novel amphiphilic block copolymers with a narrow molecular weight distribution were obtained. 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1873,1882, 2005 [source]


In situ Fourier transform near infrared spectroscopy monitoring of copper mediated living radical polymerization

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2004
Vincent Darcos
Abstract In situ Fourier transform near infrared (FTNIR) spectroscopy was successfully used to monitor monomer conversion during copper mediated living radical polymerization with N -(n -propyl)-2-pyridylmethanimine as a ligand. The conversion of vinyl protons in methacrylic monomers (methyl methacrylate, butyl methacrylate, and N -hydroxysuccinimide methacrylate) to methylene protons in the polymer was monitored with an inert fiber-optic probe. The monitoring of a poly(butyl methacrylate- b -methyl methacrylate- b -butyl methacrylate) triblock copolymer has also been reported with difunctional poly(methyl methacrylate) as a macroinitiator. In all cases FTNIR results correlated excellently with those obtained by 1H NMR. On-line near infrared (NIR) measurement was found to be more accurate because it provided many more data points and avoided sampling during the polymerization reaction. It also allowed the determination of kinetic parameters with, for example, the calculation of an apparent first-order rate constant. All the results suggest that FTNIR spectroscopy is a valuable tool to assess kinetic data. 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4933,4940, 2004 [source]


Synthesis of hydrophilic/CO2 -philic poly(ethylene oxide)- b -poly(1,1,2,2-tetrahydroperfluorodecyl acrylate) block copolymers via controlled/living radical polymerizations and their properties in liquid and supercritical CO2

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2004
Zhi Ma
Abstract Hydrophilic/CO2 -philic poly(ethylene oxide)- b -poly(1,1,2,2-tetrahydroperfluorodecyl acrylate) block copolymers were synthesized via reversible addition,fragmentation chain transfer (RAFT) polymerization, iodine transfer polymerization (ITP), and atom transfer radical polymerization (ATRP) in the presence of either degenerative transfer agents or a macroinitiator based on poly(ethylene oxide). In this work, both RAFT and ATRP showed higher efficiency than ITP for the preparation of the expected copolymers. More detailed research was carried out on RAFT, and the living character of the polymerization was confirmed by an ultraviolet (UV) analysis of the SC(S)Ph or SC(S)SC12H25 end groups in the polymer chains. The quantitative UV analysis of the copolymers indicated a number-average molecular weight in good agreement with the value determined by 1H NMR analysis. The properties of the macromolecular surfactants were investigated through the determination of the cloud points in neat liquid and supercritical CO2 and through the formation of water-in-CO2 emulsions. 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2405,2415, 2004 [source]


Synthesis of a novel hybrid liquid-crystalline rod,coil diblock copolymer

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2003
Yi Yi
Abstract A series of novel rod,coil diblock copolymers on the basis of mesogen-jacketed liquid-crystalline polymer were successfully prepared by atom transfer radical polymerization from the flexible polydimethylsiloxane (PDMS) macroinitiator. The hybrid diblock copolymers, poly{2,5-bis[(4-methoxyphenyl)oxycarbonyl]styrene}- block -polydimethylsiloxane, had number-average molecular weights (Mn's) ranging from 9500 to 30,900 and relatively narrow polydispersities (,1.34). The polymerization proceeded with first-order kinetics. Data from differential scanning calorimetry validated the microphase separation of the diblock copolymers. All block copolymers exhibited thermotropic liquid-crystalline behavior except for the one with Mn being 9500. Four liquid-crystalline diblock copolymers with PDMS weight fractions of more than 18% had two distinctive glass-transition temperatures. 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1799,1806, 2003 [source]


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

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2003
Yuhong Ma
A novel method of synthesizing a clean diblock copolymer via cationic polymerization was developed. First, a poly(4-methylstyrene) macroinitiator was prepared, and then a second comonomer (isobutene) and a coinitiator (AlEt2Cl) were added for the initiation of block copolymerization. [source]