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Minoru Terano - One of the best experts on this subject based on the ideXlab platform.
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degradation behavior of polymer blEnd of isotactic polypropylenes with and without unsaturated Chain End group
Science and Technology of Advanced Materials, 2008Co-Authors: Hisayuki Nakatani, Dodik Kurniawan, Toshiaki Taniike, Minoru TeranoAbstract:In this work, the relationship between the unsaturated Chain End group content and the thermal oxidative degradation rate was systematically studied with binary polymer blEnds of isotactic polypropylene (iPP) with and without the unsaturated Chain End group. The iPPs with and without the unsaturated Chain End group were synthesized by a metallocene catalyst in the absence of hydrogen and by a Ziegler catalyst in the presence of one, respectively. The thermal oxidative degradation rate of the binary iPP blEnds was estimated from the molecular weight and the apparent activation energy (ΔE), which were obtained through size exclusion chromatography (SEC) and thermogravimetric analysis (TGA) measurements, respectively. These values exhibited a negative correlation against the mole content of the unsaturated Chain End group. The thermal oxidative degradation rate apparently depEnds on the content of the unsaturated Chain End group. This tEndency suggests that the unsaturated Chain End acts as a radical initiator of the iPP degradation reaction.
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Effect of unsaturated Chain End‐group on thermal oxidative behavior of polypropylene
Polymer International, 2007Co-Authors: Hisayuki Nakatani, Shoutarou Suzuki, Takamasa Tanaka, Minoru TeranoAbstract:In order to clarify the influences of unsaturated Chain End-groups on the oxidative degradation of isotactic polypropylene (iPP), values of activation energy (ΔE) for the oxidative degradation reactions of Ziegler-catalyzed iPP (ZiPP) and metallocene-catalyzed iPP (MiPP) having similar tacticity were evaluated by the temperature depEndence of the oxidation induction time as determined by thermogravimetric analysis over the range 130–145 °C. The correlation between the content of unsaturated Chain End-groups and the change of ΔE was also studied. The results obtained indicated that the unsaturated Chain End-groups strongly influenced the rate of iPP degradation. Moreover, on addition of oligomer-like MiPP having unsaturated Chain End-groups, the ΔE value of ZiPP became lower, suggesting that iPP having unsaturated Chain End-groups served as an infectious agent of the degradation. Copyright © 2007 Society of Chemical Industry
David J. Lunn - One of the best experts on this subject based on the ideXlab platform.
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desulfurization bromination direct Chain End modification of raft polymers
Polymer Chemistry, 2017Co-Authors: In-hwan Lee, David J. Lunn, Emre H. Discekici, Javier Read De Alaniz, Craig J. Hawker, Athina Anastasaki, Shelby L. ShankelAbstract:We report a simple and efficient transformation of thiol and thiocarbonylthio functional groups to bromides using stable and commercially available brominating reagents. This procedure allows for the quantitative conversion of a range of small molecule thiols (including primary, secondary and tertiary) to the corresponding bromides under mild conditions, as well as the facile Chain-End modification of polystyrene (PS) homopolymers and block copolymers prepared by reversible addition-fragmentation Chain transfer (RAFT) polymerization. Specifically, the direct Chain-End bromination of PS prepared by RAFT was achieved, where the introduced terminal bromide remained active for subsequent modification or Chain-extension using classical atom transfer radical polymerization (ATRP). This transformation sets the foundation for bridging RAFT and ATRP, two of the most widely used controlled radical polymerization (CRP) strategies, and enables the preparation of Chain-End functionalized block copolymers not directly accessible using a single CRP technique.
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Desulfurization–bromination: direct Chain-End modification of RAFT polymers
Polymer chemistry, 2017Co-Authors: In-hwan Lee, Emre H. Discekici, Javier Read De Alaniz, Craig J. Hawker, Athina Anastasaki, Shelby L. Shankel, David J. LunnAbstract:We report a simple and efficient transformation of thiol and thiocarbonylthio functional groups to bromides using stable and commercially available brominating reagents. This procedure allows for the quantitative conversion of a range of small molecule thiols (including primary, secondary and tertiary) to the corresponding bromides under mild conditions, as well as the facile Chain-End modification of polystyrene (PS) homopolymers and block copolymers prepared by reversible addition-fragmentation Chain transfer (RAFT) polymerization. Specifically, the direct Chain-End bromination of PS prepared by RAFT was achieved, where the introduced terminal bromide remained active for subsequent modification or Chain-extension using classical atom transfer radical polymerization (ATRP). This transformation sets the foundation for bridging RAFT and ATRP, two of the most widely used controlled radical polymerization (CRP) strategies, and enables the preparation of Chain-End functionalized block copolymers not directly accessible using a single CRP technique.
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Practical Chain‐End Reduction of Polymers Obtained with ATRP
Macromolecular Chemistry and Physics, 2017Co-Authors: Will R. Gutekunst, David J. Lunn, Athina Anastasaki, Nghia P. Truong, Richard Whitfield, Glen R. Jones, Nicolas J. Treat, Allison Abdilla, Bryan E. Barton, Paul G. ClarkAbstract:A practical and user-friEndly strategy for the Chain-End reduction of halogen terminated polymers that employs hydrogen gas and heterogeneous catalysis (palladium on carbon) is reported. Quantitative dehalogenation of a wide variety of monomer families (polystyrenes, polyacrylates, and polymethacrylates) with either chlorine or bromine Chain-Ends is observed. The utility of this Chain-End reduction is further highlighted by mild reaction conditions, simple purification, and compatibility with a wide range of solvents. (Figure presented.).
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Established and emerging strategies for polymer Chain-End modification
Journal of Polymer Science Part A: Polymer Chemistry, 2017Co-Authors: David J. Lunn, Emre H. Discekici, Javier Read De Alaniz, Will R. Gutekunst, Craig J. HawkerAbstract:The development of “controlled” and “living” polymerization processes with high End-group fidelity has enabled an unprecedented range of polymeric materials with specific Chain-End functionality to be prepared. This highlight provides an overview of available strategies and evaluation of recent approaches for the Chain-End functionalization of polymers prepared through controlled Chain-growth polymerizations. As a tribute to Professor Robert B. Grubbs on the occasion of his 75th birthday, we also take this opportunity to highlight methods for the Chain-End modification of polymers prepared by ring-opening metathesis polymerization within the broader context of functional group tolerant, living polymerizations. Finally, we focus attention toward new directions in polymer Chain-End modifications, describing existing gaps in current strategies, and detailing recently reported protocols that show significant improvements over traditional methods. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2903–2914
Hisayuki Nakatani - One of the best experts on this subject based on the ideXlab platform.
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degradation behavior of polymer blEnd of isotactic polypropylenes with and without unsaturated Chain End group
Science and Technology of Advanced Materials, 2008Co-Authors: Hisayuki Nakatani, Dodik Kurniawan, Toshiaki Taniike, Minoru TeranoAbstract:In this work, the relationship between the unsaturated Chain End group content and the thermal oxidative degradation rate was systematically studied with binary polymer blEnds of isotactic polypropylene (iPP) with and without the unsaturated Chain End group. The iPPs with and without the unsaturated Chain End group were synthesized by a metallocene catalyst in the absence of hydrogen and by a Ziegler catalyst in the presence of one, respectively. The thermal oxidative degradation rate of the binary iPP blEnds was estimated from the molecular weight and the apparent activation energy (ΔE), which were obtained through size exclusion chromatography (SEC) and thermogravimetric analysis (TGA) measurements, respectively. These values exhibited a negative correlation against the mole content of the unsaturated Chain End group. The thermal oxidative degradation rate apparently depEnds on the content of the unsaturated Chain End group. This tEndency suggests that the unsaturated Chain End acts as a radical initiator of the iPP degradation reaction.
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Effect of unsaturated Chain End‐group on thermal oxidative behavior of polypropylene
Polymer International, 2007Co-Authors: Hisayuki Nakatani, Shoutarou Suzuki, Takamasa Tanaka, Minoru TeranoAbstract:In order to clarify the influences of unsaturated Chain End-groups on the oxidative degradation of isotactic polypropylene (iPP), values of activation energy (ΔE) for the oxidative degradation reactions of Ziegler-catalyzed iPP (ZiPP) and metallocene-catalyzed iPP (MiPP) having similar tacticity were evaluated by the temperature depEndence of the oxidation induction time as determined by thermogravimetric analysis over the range 130–145 °C. The correlation between the content of unsaturated Chain End-groups and the change of ΔE was also studied. The results obtained indicated that the unsaturated Chain End-groups strongly influenced the rate of iPP degradation. Moreover, on addition of oligomer-like MiPP having unsaturated Chain End-groups, the ΔE value of ZiPP became lower, suggesting that iPP having unsaturated Chain End-groups served as an infectious agent of the degradation. Copyright © 2007 Society of Chemical Industry
Julien Nicolas - One of the best experts on this subject based on the ideXlab platform.
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nitroxide mediated radical ring opening copolymerization Chain End investigation and block copolymer synthesis
Macromolecular Rapid Communications, 2014Co-Authors: Vianney Delplace, Didier Gigmes, Yohann Guillaneuf, Simon Harrisson, Antoine Tardy, Julien NicolasAbstract:Well-defined, degradable copolymers are successfully prepared by nitroxide-mediated radical ring opening polymerization (NMrROP) of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) or methyl methacrylate (MMA), a small amount of acrylonitrile (AN) and cyclic ketene acetals (CKAs) of different structures. Phosphorous nuclear magnetic resonance allows in-depth Chain-End characterization and gives crucial insights into the nature of the copolymer terminal sequences and the living Chain fractions. By using a small library of P(OEGMA-co-AN-co-CKA) and P(MMA-co-AN-co-CKA) as macroinitiators, Chain extensions with styrene are performed to furnish (amphiphilic) block copolymers comprising a degradable segment.
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Nitroxide-Mediated Radical Ring-Opening Copolymerization: Chain-End Investigation and Block Copolymer Synthesis
Macromolecular Rapid Communications, 2014Co-Authors: Vianney Delplace, Didier Gigmes, Yohann Guillaneuf, Simon Harrisson, Antoine Tardy, Julien NicolasAbstract:Well-defined, degradable copolymers are successfully prepared by nitroxide-mediated radical ring opening polymerization (NMrROP) of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) or methyl methacrylate (MMA), a small amount of acrylonitrile (AN) and cyclic ketene acetals (CKAs) of different structures. Phosphorous nuclear magnetic resonance allows in-depth Chain-End characterization and gives crucial insights into the nature of the copolymer terminal sequences and the living Chain fractions. By using a small library of P(OEGMA-co-AN-co-CKA) and P(MMA-co-AN-co-CKA) as macroinitiators, Chain extensions with styrene are performed to furnish (amphiphilic) block copolymers comprising a degradable segment. \textlessboxed-text content-type="graphic" position="anchor"\textgreater \textlessgraphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="urn:x-wiley:10221352:media:marc201300809:marc201300809-abs-0 001"\textgreaterimage\textless/graphic
Krzysztof Matyjaszewski - One of the best experts on this subject based on the ideXlab platform.
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how fast can a crp be conducted with preserved Chain End functionality
Macromolecules, 2011Co-Authors: Mingjiang Zhong, Krzysztof MatyjaszewskiAbstract:The preservation of Chain End functionality (CEF) is perhaps the most important criterion of the “livingness” for any controlled/living radical polymerization (CRP) system. CEF depEnds on several parameters but most importantly on concentration of propagating radicals, i.e., rate of polymerization. There are claims in the literature about ultrafast CRP leading to ultrahigh molecular weight with perfectly preserved CEF. However, faster CRP always results in lower CEF. Thus, how fast can a CRP be conducted with preserved CEF? In this paper we evaluate, by kinetic analysis and computation, the depEndence of CEF on the rate of polymerization, monomer structure (rate constants of propagation and termination), targeted degree of polymerization, initial monomer concentration, and monomer conversion. Some subtle differences in the definition of CEF are discussed for different types of atom transfer radical polymerization (ATRP) techniques. CEF for polymer Chains with and without an α-alkyl group from a (macro)ini...
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polystyrene with improved Chain End functionality and higher molecular weight by arget atrp
Macromolecular Chemistry and Physics, 2008Co-Authors: Wojciech Jakubowski, Betul Kircidenizli, Roberto R Gil, Krzysztof MatyjaszewskiAbstract:The bromine Chain-End functionality of polystyrene (PSt) prepared by activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) was analyzed using 500 MHz 1 H nuclear magnetic resonance (NMR). Bulk polymerization of styrene (St) was carried out with 50 ppm of copper in the presence of tris[2-(dimethylamino)ethyl]amine (Me 6 TREN) ligand and tin(II) 2-ethylhexanoate [Sn(EH) 2 ] reducing agent at 90 °C. Due to the use of a low concentration of an active Cu/ligand catalyst complex, it was possible to significantly decrease the occurrence of catalyst-based side reactions (β-H elimination). As a result, compared to PSt prepared via normal ATRP, PSt with improved Chain-End functionality was obtained. For example, at 92% monomer conversion in normal ATRP only 48% of Chains retained Chain-End functionality, whereas 87% of the Chains in an ARGET ATRP still contained halogen functionality. PSt with controlled molecular weight (M n,NMR = 11600 g mol -1 , M n,theor. = 9 600 g mol -1 ) and narrow molecular weight distribution (M w /M n = 1.14) was prepared under these conditions. In addition, as a result of decreased frequency of side reactions in ARGET ATRP, PSt with relatively high molecular weight was successfully prepared (M n,GPC = 185 000 g · mol -1 , M w /M n = 1.35).
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Kinetic modeling of the Chain‐End functionality in atom transfer radical polymerization
Macromolecular Chemistry and Physics, 2002Co-Authors: Jean-françois Lutz, Krzysztof MatyjaszewskiAbstract:The evolution of Chain-End functionality of polymers synthesized by atom transfer radical polymerization (ATRP) was modeled. By comparing various kinetic models, the effect of specific side reactions was estimated. The slow elimination of hydrobromic acid from the polymer End-groups as well as the thermal self-initiation of the monomer may affect the Chain-End functionality. Although the polymerization possesses several characters of a living process (i.e. linear increase of molecular weight versus conversion, low polydispersity index), the final polymer may have a limited functionality. However, polymers with enhanced functionality can be prepared through adjusting certain experimental parameters such as conversion of the monomer or initial concentration of the reactants.