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Nikos Hadjichristidis - One of the best experts on this subject based on the ideXlab platform.
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Polymethylene-Based Eight-Shaped Cyclic Block Copolymers
Macromolecules, 2019Co-Authors: Yu Jiang, Nikos HadjichristidisAbstract:A new strategy was developed for the synthesis of well-defined eight-shaped Polymethylene (PM, equivalent to polyethylene)-based cyclic block copolymers, [c-(PM-b-PCL)]2, according to the following...
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well defined Polymethylene based block co terpolymers by combining anthracene maleimide diels alder reaction with polyhomologation
Polymer Chemistry, 2015Co-Authors: Nazeeha Alkayal, Nikos HadjichristidisAbstract:A novel strategy towards well-defined Polymethylene-based co/terpolymers, by combining the anthracene/maleimide Diels–Alder reaction with polyhomologation, is presented. For the synthesis of diblock copolymers the following approach was applied: (a) synthesis of α-anthracene-ω-hydroxy-Polymethylene by polyhomologation using tri(9-anthracene-methyl propyl ether)borane as the initiator, (b) synthesis of furan-protected-maleimide-terminated poly(e-caprolactone) or polyethylene glycol and (c) the Diels–Alder reaction between the anthracene and maleimide-terminated polymers. In the case of triblock terpolymers the α-anthracene-ω-hydroxy-Polymethylene was used as a macroinitiator for the ring-opening polymerization of D,L-lactide to afford an anthracene-terminated PM-b-PLA copolymer, followed by the Diels–Alder reaction with furan-protected maleimide-terminated poly (e-caprolactone) or polyethylene glycol to give the triblock terpolymers. All the intermediates and final products were characterized by SEC, 1H NMR, UV-VIS spectroscopy and DSC.
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Well-defined Polymethylene-based block co/terpolymers by combining anthracene/maleimide diels–alder reaction with polyhomologation
Polymer Chemistry, 2015Co-Authors: Nazeeha Alkayal, Nikos HadjichristidisAbstract:A novel strategy towards well-defined Polymethylene-based co/terpolymers, by combining the anthracene/maleimide Diels–Alder reaction with polyhomologation, is presented. For the synthesis of diblock copolymers the following approach was applied: (a) synthesis of α-anthracene-ω-hydroxy-Polymethylene by polyhomologation using tri(9-anthracene-methyl propyl ether)borane as the initiator, (b) synthesis of furan-protected-maleimide-terminated poly(e-caprolactone) or polyethylene glycol and (c) the Diels–Alder reaction between the anthracene and maleimide-terminated polymers. In the case of triblock terpolymers the α-anthracene-ω-hydroxy-Polymethylene was used as a macroinitiator for the ring-opening polymerization of D,L-lactide to afford an anthracene-terminated PM-b-PLA copolymer, followed by the Diels–Alder reaction with furan-protected maleimide-terminated poly (e-caprolactone) or polyethylene glycol to give the triblock terpolymers. All the intermediates and final products were characterized by SEC, 1H NMR, UV-VIS spectroscopy and DSC.
Kiyotaka Shigehara - One of the best experts on this subject based on the ideXlab platform.
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Thermotropic Behavior of Syndiotactic Polymethylenes with ω‑[4‑(trans-4-Pentylcyclohexyl)phenoxy]alkyloxycarbonyl Side Chains
2015Co-Authors: Noboru Koshimizu, Kazuhiro Shikinaka, Koichi Sakajiri, Sungmin Kang, Kiyotaka Shigehara, Yosuke Aizawa, Masatoshi TokitaAbstract:A series of syndiotatic P5CPn Polymethylenes was prepared with 4-(trans-4-pentylcyclohexyl)phenoxy moieties linked to each backbone carbon atom via an alkyloxycarbonyl spacer and with even numbers of alkyl carbons n ranging from 2 to 14, and their thermotropic behaviors were investigated. The P5CPn, except P5CP2, formed smectic phases in which the rod-like Polymethylene backbones were arranged in rectangular lattices, and the side-chain mesogens were aggregated into layers parallel to the shorter sides of the rectangular lattices. The packing of the mesogens changed with decreasing temperature from smectic C-like to smectic I-like (SmI-like) for n = 4–8 and from smectic A-like to SmI-like for n = 10–14. In the SmI-like phases, each mesogen along the main-chain axis was connected to every sixth backbone carbon atom, revealing a correlation between the packing of the mesogens and the main-chain conformation of a 3/2 helix. Conversely, P5CP2 formed a smectic phase with the main chains arranged in rows and with the mesogens barely aggregated into layers due to the short spacers
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Thermotropic behavior of syndiotactic Polymethylenes with alkyloxycarbonyl side chains
Polymer, 2013Co-Authors: Masatoshi Tokita, Kazuhiro Shikinaka, Teruki Hoshino, Kyohei Fujii, Jun Mikami, Noboru Koshimizu, Koichi Sakajiri, Sungmin Kang, Junji Watanabe, Kiyotaka ShigeharaAbstract:Abstract A series of syndiotactic Polymethylenes having an alkyloxycarbonyl side chain, with the alkyl carbon numbers 2, 6, 12, and 18 at every main-chain carbon atom, was synthesized by rhodium complex-catalyzed stereo-selective polymerization. Differential scanning calorimetry (DSC) and X-ray diffraction revealed that all polymers formed thermotropic liquid crystalline phases. The Polymethylene having an ethoxycarbonyl side chain formed a nematic phase whereas those having hexyloxy-, dodecyloxy-, and octadecyloxy-carbonyl side chains formed hexagonal columnar phases. The tendency of these polymers to form liquid crystalline phases is due to the rod-like helical conformation in the polymer backbone, which is estimated to be seven units per two turns (7/2) with a unit height of 1.05 4 A along the helix axis.
Masatoshi Tokita - One of the best experts on this subject based on the ideXlab platform.
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Thermotropic Behavior of Syndiotactic Polymethylenes with ω‑[4‑(trans-4-Pentylcyclohexyl)phenoxy]alkyloxycarbonyl Side Chains
2015Co-Authors: Noboru Koshimizu, Kazuhiro Shikinaka, Koichi Sakajiri, Sungmin Kang, Kiyotaka Shigehara, Yosuke Aizawa, Masatoshi TokitaAbstract:A series of syndiotatic P5CPn Polymethylenes was prepared with 4-(trans-4-pentylcyclohexyl)phenoxy moieties linked to each backbone carbon atom via an alkyloxycarbonyl spacer and with even numbers of alkyl carbons n ranging from 2 to 14, and their thermotropic behaviors were investigated. The P5CPn, except P5CP2, formed smectic phases in which the rod-like Polymethylene backbones were arranged in rectangular lattices, and the side-chain mesogens were aggregated into layers parallel to the shorter sides of the rectangular lattices. The packing of the mesogens changed with decreasing temperature from smectic C-like to smectic I-like (SmI-like) for n = 4–8 and from smectic A-like to SmI-like for n = 10–14. In the SmI-like phases, each mesogen along the main-chain axis was connected to every sixth backbone carbon atom, revealing a correlation between the packing of the mesogens and the main-chain conformation of a 3/2 helix. Conversely, P5CP2 formed a smectic phase with the main chains arranged in rows and with the mesogens barely aggregated into layers due to the short spacers
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Thermotropic behavior of syndiotactic Polymethylenes with alkyloxycarbonyl side chains
Polymer, 2013Co-Authors: Masatoshi Tokita, Kazuhiro Shikinaka, Teruki Hoshino, Kyohei Fujii, Jun Mikami, Noboru Koshimizu, Koichi Sakajiri, Sungmin Kang, Junji Watanabe, Kiyotaka ShigeharaAbstract:Abstract A series of syndiotactic Polymethylenes having an alkyloxycarbonyl side chain, with the alkyl carbon numbers 2, 6, 12, and 18 at every main-chain carbon atom, was synthesized by rhodium complex-catalyzed stereo-selective polymerization. Differential scanning calorimetry (DSC) and X-ray diffraction revealed that all polymers formed thermotropic liquid crystalline phases. The Polymethylene having an ethoxycarbonyl side chain formed a nematic phase whereas those having hexyloxy-, dodecyloxy-, and octadecyloxy-carbonyl side chains formed hexagonal columnar phases. The tendency of these polymers to form liquid crystalline phases is due to the rod-like helical conformation in the polymer backbone, which is estimated to be seven units per two turns (7/2) with a unit height of 1.05 4 A along the helix axis.
J. Greaves - One of the best experts on this subject based on the ideXlab platform.
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Polyhomologation. A Living Polymethylene Synthesis
Journal of the American Chemical Society, 1997Co-Authors: Kenneth J. Shea, J. W. Walker, Huide Zhu, Manuel M. Paz, J. GreavesAbstract:The linear hydrocarbon Polymethylene differs from polyethylene in that the polymer chain is built up one carbon at a time. Polymethylene has been synthesized by the catalyzed polymerization of diazomethane.1 We report a new polymerization reaction, polyhomologation, for the synthesis of Polymethylene. The reaction utilizes methodology developed for the homologation of organoboranes. Application of this chemistry to polymer synthesis is unprecedented.
Kazuhiro Shikinaka - One of the best experts on this subject based on the ideXlab platform.
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Thermotropic Behavior of Syndiotactic Polymethylenes with ω‑[4‑(trans-4-Pentylcyclohexyl)phenoxy]alkyloxycarbonyl Side Chains
2015Co-Authors: Noboru Koshimizu, Kazuhiro Shikinaka, Koichi Sakajiri, Sungmin Kang, Kiyotaka Shigehara, Yosuke Aizawa, Masatoshi TokitaAbstract:A series of syndiotatic P5CPn Polymethylenes was prepared with 4-(trans-4-pentylcyclohexyl)phenoxy moieties linked to each backbone carbon atom via an alkyloxycarbonyl spacer and with even numbers of alkyl carbons n ranging from 2 to 14, and their thermotropic behaviors were investigated. The P5CPn, except P5CP2, formed smectic phases in which the rod-like Polymethylene backbones were arranged in rectangular lattices, and the side-chain mesogens were aggregated into layers parallel to the shorter sides of the rectangular lattices. The packing of the mesogens changed with decreasing temperature from smectic C-like to smectic I-like (SmI-like) for n = 4–8 and from smectic A-like to SmI-like for n = 10–14. In the SmI-like phases, each mesogen along the main-chain axis was connected to every sixth backbone carbon atom, revealing a correlation between the packing of the mesogens and the main-chain conformation of a 3/2 helix. Conversely, P5CP2 formed a smectic phase with the main chains arranged in rows and with the mesogens barely aggregated into layers due to the short spacers
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Thermotropic behavior of syndiotactic Polymethylenes with alkyloxycarbonyl side chains
Polymer, 2013Co-Authors: Masatoshi Tokita, Kazuhiro Shikinaka, Teruki Hoshino, Kyohei Fujii, Jun Mikami, Noboru Koshimizu, Koichi Sakajiri, Sungmin Kang, Junji Watanabe, Kiyotaka ShigeharaAbstract:Abstract A series of syndiotactic Polymethylenes having an alkyloxycarbonyl side chain, with the alkyl carbon numbers 2, 6, 12, and 18 at every main-chain carbon atom, was synthesized by rhodium complex-catalyzed stereo-selective polymerization. Differential scanning calorimetry (DSC) and X-ray diffraction revealed that all polymers formed thermotropic liquid crystalline phases. The Polymethylene having an ethoxycarbonyl side chain formed a nematic phase whereas those having hexyloxy-, dodecyloxy-, and octadecyloxy-carbonyl side chains formed hexagonal columnar phases. The tendency of these polymers to form liquid crystalline phases is due to the rod-like helical conformation in the polymer backbone, which is estimated to be seven units per two turns (7/2) with a unit height of 1.05 4 A along the helix axis.