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Low Polydispersity (low + polydispersity)
Selected AbstractsA Bimetallic Ruthenium Complex as a Catalyst Precursor for the Atom Transfer Radical Polymerization of Methacrylates at Ambient TemperatureADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4-5 2006Michel 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] Facile syntheses, morphologies, and optical absorptions of P3HT coil-rod-coil triblock copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2010Herman Lim Abstract Here we report syntheses, photophysical properties, and morphologies of a series of coil-rod-coil ABA triblock copolymers containing highly regioregular poly(3-hexylthiophene) (P3HT) as the central rod block. A new methodology, based on the coupling reaction between living polymeric anions [polystyrene, polyisoprene, and poly(methyl methacrylate)] and aldehyde terminated P3HT, was successfully developed to synthesize the triblock copolymers with low polydispersities. This coupling reaction was effective for building blocks with a variety of molecular weights; therefore, a good variation in compositions of the triblock copolymers could be feasibly achieved. The non-P3HT coil segments and the solvents were found to exhibit noticeable effects on morphologies of the spin-coated thin films. Attachment of the coil segments to P3HT did not change the optical absorption of the P3HT segment as the block copolymers were dissolved in solution regardless the chemical structure and the molecular weight of the coil segment. Interestingly, different UV,vis absorption behaviors were observed for the spin-coated thin films of the block copolymers, which closely related to their morphologies. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3311,3322, 2010 [source] A variety of poly(m -benzamide)s with low polydispersities from inductive effect-assisted chain-growth polycondensationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2006Tomoyuki Ohishi Abstract Chain-growth polycondensation of 3-(alkylamino)benzoic acid alkyl esters 1 was investigated for obtaining poly(m -benzamide)s with defined molecular weights and low polydispersities. Polymerization conditions were first studied to find that ethyl 3-(octylamino)benzoate (1b) polymerized in a chain polymerization manner in the presence of lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) as a base and phenyl 4-methylbenzoate (2b) as an initiator in THF at 0 °C. The molecular weight of the polymer was controlled by the feed ratio of monomer to initiator. The polymerization of 1c,i with a variety of N -alkyl groups was then carried out under the established conditions to yield well-defined poly(m -benzamide)s, which showed higher solubility than those of the corresponding poly(p -benzamide)s. Furthermore, the 4-octyloxybenzyl group on the amide nitrogen in poly1i was removed by treatment with trifluoroacetic acid (TFA) to give N -unsubstituted poly(m -benzamide) (poly1j) with a low polydispersity, which is soluble in DMAc and DMSO, contrary to the para-substituted counterpart. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4990,5003, 2006 [source] Synthesis and properties of biomimetic poly(L -glutamate)- b -poly(2-acryloyloxyethyllactoside)- b -poly(L -glutamate) triblock copolymersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2004Chang-Ming Dong Abstract A novel class of biomimetic glycopolymer,polypeptide triblock copolymers [poly(L -glutamate),poly(2-acryloyloxyethyllactoside),poly(L -glutamate)] was synthesized by the sequential atom transfer radical polymerization of a protected lactose-based glycomonomer and the ring-opening polymerization of ,-benzyl- L -glutamate N -carboxyanhydride. Gel permeation chromatography and nuclear magnetic resonance analyses demonstrated that triblock copolymers with defined architectures, controlled molecular weights, and low polydispersities were successfully obtained. Fourier transform infrared spectroscopy of the triblock copolymers revealed that the ,-helix/,-sheet ratio increased with the poly(benzyl- L -glutamate) block length. Furthermore, the water-soluble triblock copolymers self-assembled into lactose-installed polymeric aggregates; this was investigated with the hydrophobic dye solubilization method and ultraviolet,visible analysis. Notably, this kind of aggregate may be useful as an artificial polyvalent ligand in the investigation of carbohydrate,protein recognition and for the design of site-specific drug-delivery systems. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5754,5765, 2004 [source] Polymer,silicate nanocomposites produced by in situ atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2004Hanying Zhao Abstract Polymer,silicate nanocomposites were synthesized with atom transfer radical polymerization (ATRP). An ATRP initiator, consisting of a quaternary ammonium salt moiety and a 2-bromo-2-methyl propionate moiety, was intercalated into the interlayer spacings of the layered silicate. Subsequent ATRP of styrene, methyl methacrylate, or n -butyl acrylate with Cu(I)X/N,N -bis(2-pyridiylmethyl) octadecylamine, Cu(I)X/N,N,N,,N,,N,-pentamethyldiethylenetriamine, or Cu(I)X/1,1,4,7,10,10-hexamethyltriethylenetetramine (X = Br or Cl) catalysts with the initiator-modified silicate afforded homopolymers with predictable molecular weights and low polydispersities, both characteristics of living radical polymerization. The polystyrene nanocomposites contained both intercalated and exfoliated silicate structures, whereas the poly(methyl methacrylate) nanocomposites were significantly exfoliated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 916,924, 2004 [source] Homopolymerizations and random copolymerizations of olefins with amino-substituted cyclopentadienylchromium complexesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2002Keiji Ogata Abstract 1-(2- N,N -Dimethylaminoethyl)-2,3,4,5-tetramethylcyclopentadienyl-chromium dichloride (1), (2- N,N -dimethylaminoethyl)cyclopentadienylchromium dichloride (6), and (2- N,N -dimethylaminoethyl)indenylchromium dichloride (7) in the presence of modified methylaluminoxane exhibit high catalytic activities for the polymerization of ethylene with random copolymerizations of ethylene with propylene, ethylene with 1-hexene, and propylene with 1-hexene. These initiators conduct polymerizations to give high molecular weight polymers with low polydispersities. However, the stereoregularities are very poor in these reactions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2759,2771, 2002 [source] Multisensitive polymers based on 2-vinylpyridine and N -isopropylacrylamide ,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2001Sebastian Wohlrab Abstract Poly(2-vinylpyridine) (P2VP) containing functionalized end groups was synthesized using nitroxyl-mediated radical polymerization with a hydroxy-functionalized stable free radical. It was shown that P2VP could be synthesized with variable molar masses and low polydispersities. The transformation of the hydroxy groups to an acrylic ester led to the formation of macromonomers. A free-radical copolymerization of these macromonomers with N -isopropylacrylamide gave a graft copolymer with a poly(N -ispopropylacrylamide) backbone and P2VP side chains. Polymers containing different amounts of the monomers were synthesized. It was possible to vary both the amount of P2VP side chains at a constant chain length of the macromonomer and the chain length at a nearly constant chain number. The behavior of the multifunctional macromolecules at different temperatures and pH values was investigated using dynamic light scattering and DSC. The macromolecules were found to retain the specific properties of the homopolymers. The hydrodynamic radii of the synthesized graft copolymers were both dependent on the temperature and pH value. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3797,3804, 2001 [source] Living Radical Polymerization of Acrylates Mediated by 1,3-Bis(2-pyridylimino)isoindolatocobalt(II) Complexes: Monitoring the Chain Growth at the MetalCHEMISTRY - A EUROPEAN JOURNAL, Issue 33 2008Björn Abstract A new type of mediator for cobalt(II)-mediated radical polymerization is reported which is based on 1,3-bis(2-pyridylimino)isoindolate (bpi) as ancillary ligand. The modular synthesis of the bis(pyridylimino)isoindoles (bpiH) employed in this work is based on the condensation of 2-aminopyridines with phthalodinitriles. Reaction of the bpiH protio-ligands with a twofold excess of cobalt(II) acetate or cobalt(II) acetylacetonate in methanol gave [Co(bpi)(OAc)], which crystallize as coordination polymers, and a series of [Co(acac)(bpi)(MeOH)], which are mononuclear octahedral complexes. Upon heating the [Co(acac)(bpi)(MeOH)] compounds to 100,°C under high vacuum, the coordinated methanol was removed to give the five-coordinate complexes [Co(acac)(bpi)]. The polymerization of methyl acrylate at 60,°C was investigated by using one molar equivalent of the relatively short-lived radical source 2,2,-azobis(4-methoxy-2,4-dimethylvaleronitrile) (V-70) as initiator (monomer/catalyst/V-70: 600:1:1). The low solubility of the acetato complexes inhibits their significant activity as mediators in this reaction, whereas the acetylacetonate complexes control the radical polymerization of methyl acrylate more effectively. The radical polymerizations of the hexacoordinate complexes did not show a linear increase in number-average molecular weight (Mn) with conversion; however, the polydispersities were relatively low (PDI=1.12,1.40). By using the pentacoordinate complexes [Co(acac)(bpi)] as mediators, a linear increase in Mn values with conversion, which were very close to the theoretical values for living systems, and very low polydispersities (PDI<1.13) were obtained. This was also achieved in the block copolymerization of methyl acrylate and n -butyl acrylate. The intermediates with the growing acrylate polymer radical (.PA) were identified by liquid injection field desorption/ionization mass spectrometry as following the general formula [Co(acac)(4-methoxy-bpi)-(MA)n -R] (MA: methyl acrylate; R: C(CH3)(CH2C(CH3)2OCH3)CN), a notion also confirmed by NMR end-group analysis. [source] Preparation of polyacrylonitrile with improved isotacticity and low polydispersityJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2010Jianguo 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 60°C 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] Water-soluble ROMP polymers from amine-functionalized norbornenesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2008Sterling F. Alfred Amines are usually not tolerated in ring-opening metathesis polymerization. This report describes the synthesis of amine-containing water-soluble polymers with low polydispersity without protection-deprotection chemistry. [source] A strategy for synthesis of ion-bonded amphiphilic miktoarm star copolymers via supramolecular macro-RAFT agentJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2008Dairen Lu Abstract Amphiphilic supramolecular miktoarm star copolymers linked by ionic bonds with controlled molecular weight and low polydispersity have been successfully synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization using an ion-bonded macromolecular RAFT agent (macro-RAFT agent). Firstly, a new tetrafunctional initiator, dimethyl 4,6-bis(bromomethyl)-isophthalate, was synthesized and used as an initiator for atom transfer radical polymerization (ATRP) of styrene to form polystyrene (PSt) containing two ester groups at the middle of polymer chain. Then, the ester groups were converted into tertiary amino groups and the ion-bonded supramolecular macro-RAFT agent was obtained through the interaction between the tertiary amino group and 2-dodecylsulfanylthiocarbonylsulfanyl-2-methyl propionic acid (DMP). Finally, ion-bonded amphiphilic miktoarm star copolymer, (PSt)2 -poly(N -isopropyl-acrylamide)2, was prepared by RAFT polymerization of N -isopropylacrylamide (NIPAM) in the presence of the supramolecular macro-RAFT agent. The polymerization kinetics was investigated and the molecular weight and the architecture of the resulting star polymers were characterized by means of 1H-NMR, FTIR, and GPC techniques. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5805,5815, 2008 [source] Copolymerization of vinyl acetate with 1-octene and ethylene by cobalt-mediated radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2007Rayna Bryaskova Abstract The cobalt-mediated radical polymerization of vinyl acetate was extended to copolymerization with 1-alkenes (ethylene or 1-octene). In agreement with the low amount of 1-alkene that could be incorporated into the copolymer, a gradient structure was predictable, but a rather low polydispersity was observed. A poly(vinyl acetate)- b -poly(octene) copolymer was also successfully synthesized, leading to a poly (vinyl alcohol)- b -poly(octene) amphiphilic copolymer upon the methanolysis of the poly (vinyl acetate) block. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2532,2542, 2007 [source] A variety of poly(m -benzamide)s with low polydispersities from inductive effect-assisted chain-growth polycondensationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 17 2006Tomoyuki Ohishi Abstract Chain-growth polycondensation of 3-(alkylamino)benzoic acid alkyl esters 1 was investigated for obtaining poly(m -benzamide)s with defined molecular weights and low polydispersities. Polymerization conditions were first studied to find that ethyl 3-(octylamino)benzoate (1b) polymerized in a chain polymerization manner in the presence of lithium 1,1,1,3,3,3-hexamethyldisilazide (LiHMDS) as a base and phenyl 4-methylbenzoate (2b) as an initiator in THF at 0 °C. The molecular weight of the polymer was controlled by the feed ratio of monomer to initiator. The polymerization of 1c,i with a variety of N -alkyl groups was then carried out under the established conditions to yield well-defined poly(m -benzamide)s, which showed higher solubility than those of the corresponding poly(p -benzamide)s. Furthermore, the 4-octyloxybenzyl group on the amide nitrogen in poly1i was removed by treatment with trifluoroacetic acid (TFA) to give N -unsubstituted poly(m -benzamide) (poly1j) with a low polydispersity, which is soluble in DMAc and DMSO, contrary to the para-substituted counterpart. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4990,5003, 2006 [source] Controlled radical polymerization of a trialkylsilyl methacrylate by reversible addition,fragmentation chain transfer polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2005M. N. Nguyen Abstract The reversible addition,fragmentation chain transfer (RAFT) polymerization of a hydrolyzable monomer (tert -butyldimethylsilyl methacrylate) with cumyl dithiobenzoate and 2-cyanoprop-2-yl dithiobenzoate as chain-transfer agents was studied in toluene solutions at 70 °C. The resulting homopolymers had low polydispersity (polydispersity index < 1.3) up to 96% monomer conversion with molecular weights at high conversions close to the theoretical prediction. The profiles of the number-average molecular weight versus the conversion revealed controlled polymerization features with chain-transfer constants expected between 1.0 and 10. A series of poly(tert -butyldimethylsilyl methacrylate)s were synthesized over the molecular weight range of 1.0 × 104 to 3.0 × 104, as determined by size exclusion chromatography. As strong differences of hydrodynamic volumes in tetrahydrofuran between poly(methyl methacrylate), polystyrene standards, and poly(tert -butyldimethylsilyl methacrylate) were observed, true molecular weights were obtained from a light scattering detector equipped in a triple-detector size exclusion chromatograph. The Mark,Houwink,Sakurada parameters for poly(tert -butyldimethylsilyl methacrylate) were assessed to obtain directly true molecular weight values from size exclusion chromatography with universal calibration. In addition, a RAFT agent efficiency above 94% was confirmed at high conversions by both light scattering detection and 1H NMR spectroscopy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5680,5689, 2005 [source] Fast Synthesis of Nanostructured Microspheres of a Bridged Silsesquioxane via Ultrasound-Assisted Sol,Gel ProcessingMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2009Hernán E. Romeo Abstract Microspheres of a nanostructured bridged silsesquioxane were synthesized by employing ultrasound-assisted self-assembly of a bridged monomer via sol,gel processing. The bridged precursor was synthesized from glycidoxypropyl(trimethoxysilane) (GPMS) (2 mol) and cyclohexylamine (1 mol). The main factor controlling the generation of a stable dispersion of microspheres was the time at which the phase separation of the silsesquioxane was produced during the hydrolytic condensation. An appropriate blend of THF/n -hexane as a solvent enabled to rapidly generate a stable dispersion exhibiting a low polydispersity. The mild reaction conditions produced the nanostructuring of the silsesquioxane characterized by a fine structure in SAXS spectrum. Inorganic domains were arranged in a two-dimensional hexagonal system leading to the formation of cavities in the microspheres which could be employed as host,guest systems in advanced technologies. [source] Synthesis and Characterization of Styrene/Butyl Acrylate Linear and Star Block Copolymers via Atom Transfer Radical PolymerizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 9 2006Jinyu 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] Formation of Inorganic/Organic Nanocomposites by Nitroxide-Mediated Polymerization in Bulk Using a Bimolecular SystemMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 10 2004Julien Parvole Abstract Summary: A series of organic-inorganic nanoparticles were synthesized by nitroxide-mediated polymerization (NMP) of butyl acrylate initiated by a self-assembled monolayer of an azo initiator. The azo initiator was immobilized on silica particles in the presence of a stable nitroxide radical, SG1 (an acyclic , -phosphonylated nitroxide, N - tert -butyl- N -(1-diethylphosphono-2,2-dimethyl)propyl nitroxide). After preliminary qualitative characterization by X-ray spectroscopy (XPS) and Fourier-transform infrared (FTIR) measurements, the nanoparticles were studied by thermogravimetric analysis (TGA) to determine the polymer grafting density and to permit a comparison with corresponding values of the initiator monolayer. It was demonstrated that the grafting from polymerization exhibits a controlled character with a low polydispersity (,<,1.2) in a large range of molecular weights of the grafted chains (from 4,000 up to 145,000 g,·,mol,1) under the conditions when the stable radical SG1, acting as chain growth moderator tethered to the inorganic core, was used. [source] Synthesis of Well-Defined Rod-Coil Diblock Copolymer of Aromatic Polyether and Polyacrylonitrile by Chain-Growth Condensation Polymerization and Atom Transfer Radical PolymerizationMACROMOLECULAR RAPID COMMUNICATIONS, Issue 8 2008Naomi 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] Synthesis of well-defined poly(p -benzamide) from chain-growth polycondensation and its application to block copolymersMACROMOLECULAR SYMPOSIA, Issue 1 2003Tsutomu Yokozawa Abstract Poly(p -benzamide) with a defined molecular weight and a low polydispersity and block copolymers containing this well-defined aramide was synthesized. Phenyl 4-(4-octyloxybenzylamino)benzoate (1b) polymerized at room temperature in the presence of base and phenyl 4-nitrobenzoate (2a) as an initiator in a chain-growth polycondensation manner to give well-defined aromatic polyamides having the 4-octyloxybenzyl groups as a protecting group on nitrogen in an amide. It was confirmed by a model reaction that deprotection of this protecting group proceeded completely with trifluoroacetic acid (TFA) without breaking the amide linkage. The utility of this approach to poly(p -benzamide) with a low polydispersity was demonstrated by the synthesis of block copolymers of poly(p -benzamide) and poly(N -octyl- p -benzamide) or poly(ethylene glycol). The SEM images of the supramolecular assemblies of the former block copolymer showed ,m-sized bundles and aggregates of flake structures. [source] Surface-initiated nitroxide-mediated polymerization: a tool for hybrid inorganic/organic nanocomposites ,in situ' synthesisPOLYMER INTERNATIONAL, Issue 10 2006Leïla Ghannam Abstract Hybrid silica particles comprised of an inorganic core and an organic polymer shell can be synthesized by surface-initiated nitroxide-mediated polymerization (SINMP) in the presence of a grafted alkoxyamine as initiator. The layer of initiator molecules attached or adsorbed to the particles surface is based on a nitroxide group. The synthesis and characterization of these alkoxyamine structures are briefly described. The grafted initiator particles are studied in order to determine the nature of the anchorage sites and the grafting density. With a stable radical or nitroxide as chain-growth moderator tethered to the inorganic core, it was demonstrated that the grafting from or to SINMP exhibits a control character with a very low polydispersity and good agreement between theoretical/experimental molecular weights. A comparative review of different alkoxyamines with a bimolecular system based on a grafted azoic initiator in the presence of an acyclic ,-phosphonylated nitroxide called SG1 is also described. Moreover, original methods for the synthesis of alkoxyamine grafted surface by in situ trapping of carbon radicals and some new developments for colored pigments will be reported. These topics could be one of the directions of the field in the next years. Copyright © 2006 Society of Chemical Industry [source] | |||||||||||||