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Kohzo Ito - One of the best experts on this subject based on the ideXlab platform.
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boron nitride with high zeta potential via plasma processing in solution for preparation of Polyrotaxane composite
Journal of Physics D, 2021Co-Authors: Kenichi Inoue, Kohzo Ito, Taku Goto, Tsuyohito Ito, Yoshiki Shimizu, Yukiya Hakuta, Kazuo TerashimaAbstract:Plasma processing in solution is effective for the preparation of composites. To optimize the plasma processing in solution, a method that can be used to sufficiently evaluate the surface modifications is necessary. In this study, to identify such a method, hexagonal boron nitride (hBN) particles modified by plasma processing in solution and exhibiting different zeta potentials were used to prepare a Polyrotaxane composite. Plasma processing in a hydroquinone solution yielded hBN particles with a high zeta potential, named HQpBN, and X-ray computed tomography showed a uniform dispersion of the HQpBN/Polyrotaxane composite. The tensile strength and elongation of the HQpBN/Polyrotaxane composite were twice as high as those of an unmodified hBN/Polyrotaxane composite, in which hBN particles aggregated. These results demonstrate that the zeta potential of the modified particles can be used as an indicator to guide optimal surface modification during plasma processing in solution for the preparation of homogeneous composites.
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effects of ring size on the dynamics of Polyrotaxane glass
Macromolecules, 2020Co-Authors: Akihiro Ohara, Kazuaki Kato, Koji Michishio, Kohzo ItoAbstract:The dynamics of two Polyrotaxanes with different ring component sizes were compared through viscoelastic measurements. An improved Polyrotaxane synthesis was used to develop a glass-forming polyrot...
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viscoelastic relaxation attributed to the molecular dynamics of Polyrotaxane confined in an epoxy resin network
Polymer Journal, 2020Co-Authors: Akihiro Hanafusa, Koichi Mayumi, Shota Ando, Satoru Ozawa, Masakazu Ito, Ryuichi Hasegawa, Kohzo ItoAbstract:The molecular dynamics of Polyrotaxane (PR) dispersed homogeneously in a cross-linked epoxy resin were studied using dynamic mechanical analysis (DMA) and pulsed NMR spectroscopy. In PR, poly-e-caprolactone (PCL)-grafted α-cyclodextrins (CDs) are threaded on a polyethylene glycol (PEG) axis. At low temperatures, the PEG and PCL chains of the PR embedded in the epoxy network are in a glassy state. With increasing temperature, the PEG in the PR undergoes a glass-to-rubber transition and fluctuates in the glassy PCL-grafted CDs confined by the epoxy matrix, which causes viscoelastic relaxation. The glass transition temperature, Tg, of the PEG in the PR is much higher than that of pure PEG because of the strong confinement effect in the epoxy network. In addition, the Tg of the PEG drastically changes with coverage by the CDs on the PEG, suggesting that the topological constraint by the CDs also substantially influences the PEG dynamics. The viscoelastic relaxation ascribed to PEG enhances the deformability and toughness of the epoxy resin containing PR under uniaxial stretching. The molecular dynamics of PCL-grafted Polyrotaxanes (PRs) homogeneously dispersed in a cross-linked epoxy network were investigated using viscoelastic mechanical measurements and relaxation time measurements with pulsed NMR spectroscopy. With increasing temperature, the PEG axial chains in the PRs exhibit a glass-rubber transition and start fluctuating in the CDs with glassy PCL graft chains, which causes viscoelastic mechanical relaxation.
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molecular dynamics of Polyrotaxane in solution investigated by quasi elastic neutron scattering and molecular dynamics simulation sliding motion of rings on polymer
Journal of the American Chemical Society, 2019Co-Authors: Yusuke Yasuda, Hideaki Yokoyama, Koichi Mayumi, Yuta Hidaka, Takeshi Yamada, Kazushi Fujimoto, Susumu Okazaki, Kohzo ItoAbstract:In this study, we investigated the molecular dynamics of Polyrotaxane (PR), composed of α-cyclodextrins (CDs) and a poly(ethylene glycol) (PEG) axial chain, in solution by means of quasi-elastic ne...
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Autonomously isolated pseudo-Polyrotaxane nanosheets fabricated via hierarchically ordered supramolecular self-assembly
Chemical Communications, 2019Co-Authors: Shuntaro Uenuma, Rina Maeda, Hideaki Yokoyama, Kohzo ItoAbstract:We succeeded in obtaining autonomously isolated nanosheets consisting of pseudo-Polyrotaxane (PPR) fabricated via hierarchically ordered supramolecular self-assembly of β-cyclodextrin and a poloxamer by introducing charged groups to the axis ends of the poloxamer. The isolated PPR nanosheets exhibited a tunable structural coloration and were aligned using a strong magnetic field.
Wei-qun Shi - One of the best experts on this subject based on the ideXlab platform.
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temperature triggered structural dynamics of non coordinating guest moieties in a fluorescent actinide Polyrotaxane framework
Chemistry: A European Journal, 2021Co-Authors: Junshan Geng, Lei Mei, Zhifang Chai, Liwen Zeng, Jingyang Wang, Xianghe Kong, Ning Liu, Wei-qun ShiAbstract:We present here the synthesis of a novel fluorescent actinide Polyrotaxane compound URCP1 through the utilization of an end-cutting pseudorotaxane precursor with only the cucurbit[6]uril (CB[6]) macrocyclic components acting as linking struts. The non-coordinating guest motif in the obtained Polyrotaxane, with increased freedom and structural flexibility, can display intriguing temperature-triggered conformational variations inside the cavity of CB[6], which was clearly evidenced by crystallographic snapshots at different temperatures. Notably, this observation of temperature-triggered structural dynamics in URCP1 represents the first report of actinide Polyrotaxane with such feature in solid-state. Moreover, URCP1 has a high photoluminescence quantum yield (PLQY) of 49.8 %, comparable to other luminescent uranyl compounds, and can work as a fluorescent probe to selectively detect Fe3+ over other eight competing cations in aqueous solution, with the limit of detection being as low as 4.4×10-3 ppm.
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Template-Driven Assembly of Rare Hexameric Uranyl-Organic Rotaxane Networks Threaded on Dimeric Uranyl Chains
2018Co-Authors: Lei Mei, Zhifang Chai, Chuan-qin Xia, Wei-qun ShiAbstract:Despite the rise of uranyl-organic rotaxane compounds along with the prosperity of uranyl-organic frameworks, uranyl-based Polyrotaxane compounds with high nuclearity have been rarely reported. In this work, a novel twofold nested uranyl Polyrotaxane compound (1, [ (UO2)3O(OH)3(C4CA4@CB6)1.5]·[(UO2)(OH) (H2O) (C4CA4@CB6)0.5)]) with two different moieties, hexameric networks and dimeric chains, has been synthesized from C4CN4@CB6 (L1) using C4N4@CB6 (L3) as the induction agent. It is worth noting that the hexameric uranyl SBUs found here represent the highest nuclearity of uranyl found by far in uranyl-organic rotaxane frameworks. When starting from C4CN3@CB6, a positional isomer of C4CN4@CB6 (L2), compound 2 ([(UO2)(H2O)(NO3)(C4CA3@CB6)]·[(C4CA3@CB6)]) was obtained, which contains a one-dimensional Polyrotaxane chain linked by another set of noncoordinated C4CA3@CB6 motifs through hydrogen bonding. Further characterization of compound 1 by fluorescence, IR, and Raman spectra was performed to analyze the features of the hexameric uranyl unit as well as dimeric unit. Meanwhile, the mechanism for the formation of 1 and 2 has been proposed by a comprehensive comparison with previously reported trimeric uranyl Polyrotaxane networks, suggesting the vital role of self-template in the formation of uranyl-organic rotaxane frameworks, especially for hexameric uranyl unit in 1
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mixed ligand uranyl Polyrotaxanes incorporating a sulfate oxalate coligand achieving structural diversity via ph dependent competitive effect
Inorganic Chemistry, 2017Co-Authors: Zhenni Xie, Lei Mei, Zhifang Chai, Liang-shu Xia, Wei-qun ShiAbstract:A mixed-ligand system provides an alternative route to tune the structures and properties of metal–organic compounds by introducing functional organic or inorganic coligands. In this work, five new uranyl-based Polyrotaxane compounds incorporating a sulfate or oxalate coligand have been hydrothermally synthesized via a mixed-ligand method. Based on C6BPCA@CB6 (C6BPCA = 1,1′-(hexane-1,6-diyl)bis(4-(carbonyl)pyridin-1-ium), CB6 = cucurbit[6]uril) ligand, UPS1 (UO2(L)0.5(SO4)(H2O)·2H2O, L = C6BPCA@CB6) is formed by the alteration of initial aqueous solution pH to a higher acidity. The resulting 2D uranyl Polyrotaxane sheet structure of UPS1 is based on uranyl-sulfate ribbons connected by the C6BPCA@CB6 pseudorotaxane linkers. By using oxalate ligand instead of sulfate, four oxalate-containing uranyl Polyrotaxane compounds, UPO1–UPO4, have been acquired by tuning reaction pH and ligand concentration: UPO1 (UO2(L)0.5(C2O4)0.5(NO3)·3H2O) in one-dimensional chain was obtained at a low pH value range (1.47–1.89) ...
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Mixed-Ligand Uranyl Polyrotaxanes Incorporating a Sulfate/Oxalate Coligand: Achieving Structural Diversity via pH-Dependent Competitive Effect
2017Co-Authors: Zhenni Xie, Lei Mei, Zhifang Chai, Liang-shu Xia, Wei-qun ShiAbstract:A mixed-ligand system provides an alternative route to tune the structures and properties of metal–organic compounds by introducing functional organic or inorganic coligands. In this work, five new uranyl-based Polyrotaxane compounds incorporating a sulfate or oxalate coligand have been hydrothermally synthesized via a mixed-ligand method. Based on C6BPCA@CB6 (C6BPCA = 1,1′-(hexane-1,6-diyl)bis(4-(carbonyl)pyridin-1-ium), CB6 = cucurbit[6]uril) ligand, UPS1 (UO2(L)0.5(SO4)(H2O)·2H2O, L = C6BPCA@CB6) is formed by the alteration of initial aqueous solution pH to a higher acidity. The resulting 2D uranyl Polyrotaxane sheet structure of UPS1 is based on uranyl-sulfate ribbons connected by the C6BPCA@CB6 pseudorotaxane linkers. By using oxalate ligand instead of sulfate, four oxalate-containing uranyl Polyrotaxane compounds, UPO1–UPO4, have been acquired by tuning reaction pH and ligand concentration: UPO1 (UO2(L)0.5(C2O4)0.5(NO3)·3H2O) in one-dimensional chain was obtained at a low pH value range (1.47–1.89) and UPO2 (UO2(L)(C2O4)(H2O)·7H2O)obtained at a higher pH value range (4.31–7.21). By lowering the amount of oxalate, another two uranyl Polyrotaxane network UPO3 ((UO2)2(L)0.5(C2O4)2(H2O)) and UPO4 ((UO2)2O(OH)(L)0.5(C2O4)0.5(H2O)) could be acquired at a low pH value of 1.98 and a higher pH value over 6, respectively. The UPO1–UPO4 compounds, which display structural diversity via pH-dependent competitive effect of oxalate, represent the first series of mixed-ligand uranyl Polyrotaxanes with organic ligand as the coligand. Moreover, the self-assembly process and its internal mechanism concerning pH-dependent competitive effect and other related factors such as concentration of the reagents and coordination behaviors of the coligands were discussed in detail
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first three dimensional actinide Polyrotaxane framework mediated by windmill like six connected oligomeric uranyl dual roles of the pseudorotaxane precursor
Dalton Transactions, 2016Co-Authors: Lei Mei, Zhifang Chai, Zhenni Xie, Lin Wang, Liyong Yuan, Wei-qun ShiAbstract:The first 3D actinide Polyrotaxane framework (named IHEP-URCP-2) has been obtained based on windmill-like six-connected high-nuclear oligomeric uranyl nodes under hydrothermal conditions. Notably, the in situ formed pseudorotaxane ligand simultaneously plays dual roles of both a bulky pseudorotaxane linker and a supramolecular guest.
Zhifang Chai - One of the best experts on this subject based on the ideXlab platform.
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temperature triggered structural dynamics of non coordinating guest moieties in a fluorescent actinide Polyrotaxane framework
Chemistry: A European Journal, 2021Co-Authors: Junshan Geng, Lei Mei, Zhifang Chai, Liwen Zeng, Jingyang Wang, Xianghe Kong, Ning Liu, Wei-qun ShiAbstract:We present here the synthesis of a novel fluorescent actinide Polyrotaxane compound URCP1 through the utilization of an end-cutting pseudorotaxane precursor with only the cucurbit[6]uril (CB[6]) macrocyclic components acting as linking struts. The non-coordinating guest motif in the obtained Polyrotaxane, with increased freedom and structural flexibility, can display intriguing temperature-triggered conformational variations inside the cavity of CB[6], which was clearly evidenced by crystallographic snapshots at different temperatures. Notably, this observation of temperature-triggered structural dynamics in URCP1 represents the first report of actinide Polyrotaxane with such feature in solid-state. Moreover, URCP1 has a high photoluminescence quantum yield (PLQY) of 49.8 %, comparable to other luminescent uranyl compounds, and can work as a fluorescent probe to selectively detect Fe3+ over other eight competing cations in aqueous solution, with the limit of detection being as low as 4.4×10-3 ppm.
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Template-Driven Assembly of Rare Hexameric Uranyl-Organic Rotaxane Networks Threaded on Dimeric Uranyl Chains
2018Co-Authors: Lei Mei, Zhifang Chai, Chuan-qin Xia, Wei-qun ShiAbstract:Despite the rise of uranyl-organic rotaxane compounds along with the prosperity of uranyl-organic frameworks, uranyl-based Polyrotaxane compounds with high nuclearity have been rarely reported. In this work, a novel twofold nested uranyl Polyrotaxane compound (1, [ (UO2)3O(OH)3(C4CA4@CB6)1.5]·[(UO2)(OH) (H2O) (C4CA4@CB6)0.5)]) with two different moieties, hexameric networks and dimeric chains, has been synthesized from C4CN4@CB6 (L1) using C4N4@CB6 (L3) as the induction agent. It is worth noting that the hexameric uranyl SBUs found here represent the highest nuclearity of uranyl found by far in uranyl-organic rotaxane frameworks. When starting from C4CN3@CB6, a positional isomer of C4CN4@CB6 (L2), compound 2 ([(UO2)(H2O)(NO3)(C4CA3@CB6)]·[(C4CA3@CB6)]) was obtained, which contains a one-dimensional Polyrotaxane chain linked by another set of noncoordinated C4CA3@CB6 motifs through hydrogen bonding. Further characterization of compound 1 by fluorescence, IR, and Raman spectra was performed to analyze the features of the hexameric uranyl unit as well as dimeric unit. Meanwhile, the mechanism for the formation of 1 and 2 has been proposed by a comprehensive comparison with previously reported trimeric uranyl Polyrotaxane networks, suggesting the vital role of self-template in the formation of uranyl-organic rotaxane frameworks, especially for hexameric uranyl unit in 1
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mixed ligand uranyl Polyrotaxanes incorporating a sulfate oxalate coligand achieving structural diversity via ph dependent competitive effect
Inorganic Chemistry, 2017Co-Authors: Zhenni Xie, Lei Mei, Zhifang Chai, Liang-shu Xia, Wei-qun ShiAbstract:A mixed-ligand system provides an alternative route to tune the structures and properties of metal–organic compounds by introducing functional organic or inorganic coligands. In this work, five new uranyl-based Polyrotaxane compounds incorporating a sulfate or oxalate coligand have been hydrothermally synthesized via a mixed-ligand method. Based on C6BPCA@CB6 (C6BPCA = 1,1′-(hexane-1,6-diyl)bis(4-(carbonyl)pyridin-1-ium), CB6 = cucurbit[6]uril) ligand, UPS1 (UO2(L)0.5(SO4)(H2O)·2H2O, L = C6BPCA@CB6) is formed by the alteration of initial aqueous solution pH to a higher acidity. The resulting 2D uranyl Polyrotaxane sheet structure of UPS1 is based on uranyl-sulfate ribbons connected by the C6BPCA@CB6 pseudorotaxane linkers. By using oxalate ligand instead of sulfate, four oxalate-containing uranyl Polyrotaxane compounds, UPO1–UPO4, have been acquired by tuning reaction pH and ligand concentration: UPO1 (UO2(L)0.5(C2O4)0.5(NO3)·3H2O) in one-dimensional chain was obtained at a low pH value range (1.47–1.89) ...
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Mixed-Ligand Uranyl Polyrotaxanes Incorporating a Sulfate/Oxalate Coligand: Achieving Structural Diversity via pH-Dependent Competitive Effect
2017Co-Authors: Zhenni Xie, Lei Mei, Zhifang Chai, Liang-shu Xia, Wei-qun ShiAbstract:A mixed-ligand system provides an alternative route to tune the structures and properties of metal–organic compounds by introducing functional organic or inorganic coligands. In this work, five new uranyl-based Polyrotaxane compounds incorporating a sulfate or oxalate coligand have been hydrothermally synthesized via a mixed-ligand method. Based on C6BPCA@CB6 (C6BPCA = 1,1′-(hexane-1,6-diyl)bis(4-(carbonyl)pyridin-1-ium), CB6 = cucurbit[6]uril) ligand, UPS1 (UO2(L)0.5(SO4)(H2O)·2H2O, L = C6BPCA@CB6) is formed by the alteration of initial aqueous solution pH to a higher acidity. The resulting 2D uranyl Polyrotaxane sheet structure of UPS1 is based on uranyl-sulfate ribbons connected by the C6BPCA@CB6 pseudorotaxane linkers. By using oxalate ligand instead of sulfate, four oxalate-containing uranyl Polyrotaxane compounds, UPO1–UPO4, have been acquired by tuning reaction pH and ligand concentration: UPO1 (UO2(L)0.5(C2O4)0.5(NO3)·3H2O) in one-dimensional chain was obtained at a low pH value range (1.47–1.89) and UPO2 (UO2(L)(C2O4)(H2O)·7H2O)obtained at a higher pH value range (4.31–7.21). By lowering the amount of oxalate, another two uranyl Polyrotaxane network UPO3 ((UO2)2(L)0.5(C2O4)2(H2O)) and UPO4 ((UO2)2O(OH)(L)0.5(C2O4)0.5(H2O)) could be acquired at a low pH value of 1.98 and a higher pH value over 6, respectively. The UPO1–UPO4 compounds, which display structural diversity via pH-dependent competitive effect of oxalate, represent the first series of mixed-ligand uranyl Polyrotaxanes with organic ligand as the coligand. Moreover, the self-assembly process and its internal mechanism concerning pH-dependent competitive effect and other related factors such as concentration of the reagents and coordination behaviors of the coligands were discussed in detail
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first three dimensional actinide Polyrotaxane framework mediated by windmill like six connected oligomeric uranyl dual roles of the pseudorotaxane precursor
Dalton Transactions, 2016Co-Authors: Lei Mei, Zhifang Chai, Zhenni Xie, Lin Wang, Liyong Yuan, Wei-qun ShiAbstract:The first 3D actinide Polyrotaxane framework (named IHEP-URCP-2) has been obtained based on windmill-like six-connected high-nuclear oligomeric uranyl nodes under hydrothermal conditions. Notably, the in situ formed pseudorotaxane ligand simultaneously plays dual roles of both a bulky pseudorotaxane linker and a supramolecular guest.
Lei Mei - One of the best experts on this subject based on the ideXlab platform.
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temperature triggered structural dynamics of non coordinating guest moieties in a fluorescent actinide Polyrotaxane framework
Chemistry: A European Journal, 2021Co-Authors: Junshan Geng, Lei Mei, Zhifang Chai, Liwen Zeng, Jingyang Wang, Xianghe Kong, Ning Liu, Wei-qun ShiAbstract:We present here the synthesis of a novel fluorescent actinide Polyrotaxane compound URCP1 through the utilization of an end-cutting pseudorotaxane precursor with only the cucurbit[6]uril (CB[6]) macrocyclic components acting as linking struts. The non-coordinating guest motif in the obtained Polyrotaxane, with increased freedom and structural flexibility, can display intriguing temperature-triggered conformational variations inside the cavity of CB[6], which was clearly evidenced by crystallographic snapshots at different temperatures. Notably, this observation of temperature-triggered structural dynamics in URCP1 represents the first report of actinide Polyrotaxane with such feature in solid-state. Moreover, URCP1 has a high photoluminescence quantum yield (PLQY) of 49.8 %, comparable to other luminescent uranyl compounds, and can work as a fluorescent probe to selectively detect Fe3+ over other eight competing cations in aqueous solution, with the limit of detection being as low as 4.4×10-3 ppm.
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Template-Driven Assembly of Rare Hexameric Uranyl-Organic Rotaxane Networks Threaded on Dimeric Uranyl Chains
2018Co-Authors: Lei Mei, Zhifang Chai, Chuan-qin Xia, Wei-qun ShiAbstract:Despite the rise of uranyl-organic rotaxane compounds along with the prosperity of uranyl-organic frameworks, uranyl-based Polyrotaxane compounds with high nuclearity have been rarely reported. In this work, a novel twofold nested uranyl Polyrotaxane compound (1, [ (UO2)3O(OH)3(C4CA4@CB6)1.5]·[(UO2)(OH) (H2O) (C4CA4@CB6)0.5)]) with two different moieties, hexameric networks and dimeric chains, has been synthesized from C4CN4@CB6 (L1) using C4N4@CB6 (L3) as the induction agent. It is worth noting that the hexameric uranyl SBUs found here represent the highest nuclearity of uranyl found by far in uranyl-organic rotaxane frameworks. When starting from C4CN3@CB6, a positional isomer of C4CN4@CB6 (L2), compound 2 ([(UO2)(H2O)(NO3)(C4CA3@CB6)]·[(C4CA3@CB6)]) was obtained, which contains a one-dimensional Polyrotaxane chain linked by another set of noncoordinated C4CA3@CB6 motifs through hydrogen bonding. Further characterization of compound 1 by fluorescence, IR, and Raman spectra was performed to analyze the features of the hexameric uranyl unit as well as dimeric unit. Meanwhile, the mechanism for the formation of 1 and 2 has been proposed by a comprehensive comparison with previously reported trimeric uranyl Polyrotaxane networks, suggesting the vital role of self-template in the formation of uranyl-organic rotaxane frameworks, especially for hexameric uranyl unit in 1
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mixed ligand uranyl Polyrotaxanes incorporating a sulfate oxalate coligand achieving structural diversity via ph dependent competitive effect
Inorganic Chemistry, 2017Co-Authors: Zhenni Xie, Lei Mei, Zhifang Chai, Liang-shu Xia, Wei-qun ShiAbstract:A mixed-ligand system provides an alternative route to tune the structures and properties of metal–organic compounds by introducing functional organic or inorganic coligands. In this work, five new uranyl-based Polyrotaxane compounds incorporating a sulfate or oxalate coligand have been hydrothermally synthesized via a mixed-ligand method. Based on C6BPCA@CB6 (C6BPCA = 1,1′-(hexane-1,6-diyl)bis(4-(carbonyl)pyridin-1-ium), CB6 = cucurbit[6]uril) ligand, UPS1 (UO2(L)0.5(SO4)(H2O)·2H2O, L = C6BPCA@CB6) is formed by the alteration of initial aqueous solution pH to a higher acidity. The resulting 2D uranyl Polyrotaxane sheet structure of UPS1 is based on uranyl-sulfate ribbons connected by the C6BPCA@CB6 pseudorotaxane linkers. By using oxalate ligand instead of sulfate, four oxalate-containing uranyl Polyrotaxane compounds, UPO1–UPO4, have been acquired by tuning reaction pH and ligand concentration: UPO1 (UO2(L)0.5(C2O4)0.5(NO3)·3H2O) in one-dimensional chain was obtained at a low pH value range (1.47–1.89) ...
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Mixed-Ligand Uranyl Polyrotaxanes Incorporating a Sulfate/Oxalate Coligand: Achieving Structural Diversity via pH-Dependent Competitive Effect
2017Co-Authors: Zhenni Xie, Lei Mei, Zhifang Chai, Liang-shu Xia, Wei-qun ShiAbstract:A mixed-ligand system provides an alternative route to tune the structures and properties of metal–organic compounds by introducing functional organic or inorganic coligands. In this work, five new uranyl-based Polyrotaxane compounds incorporating a sulfate or oxalate coligand have been hydrothermally synthesized via a mixed-ligand method. Based on C6BPCA@CB6 (C6BPCA = 1,1′-(hexane-1,6-diyl)bis(4-(carbonyl)pyridin-1-ium), CB6 = cucurbit[6]uril) ligand, UPS1 (UO2(L)0.5(SO4)(H2O)·2H2O, L = C6BPCA@CB6) is formed by the alteration of initial aqueous solution pH to a higher acidity. The resulting 2D uranyl Polyrotaxane sheet structure of UPS1 is based on uranyl-sulfate ribbons connected by the C6BPCA@CB6 pseudorotaxane linkers. By using oxalate ligand instead of sulfate, four oxalate-containing uranyl Polyrotaxane compounds, UPO1–UPO4, have been acquired by tuning reaction pH and ligand concentration: UPO1 (UO2(L)0.5(C2O4)0.5(NO3)·3H2O) in one-dimensional chain was obtained at a low pH value range (1.47–1.89) and UPO2 (UO2(L)(C2O4)(H2O)·7H2O)obtained at a higher pH value range (4.31–7.21). By lowering the amount of oxalate, another two uranyl Polyrotaxane network UPO3 ((UO2)2(L)0.5(C2O4)2(H2O)) and UPO4 ((UO2)2O(OH)(L)0.5(C2O4)0.5(H2O)) could be acquired at a low pH value of 1.98 and a higher pH value over 6, respectively. The UPO1–UPO4 compounds, which display structural diversity via pH-dependent competitive effect of oxalate, represent the first series of mixed-ligand uranyl Polyrotaxanes with organic ligand as the coligand. Moreover, the self-assembly process and its internal mechanism concerning pH-dependent competitive effect and other related factors such as concentration of the reagents and coordination behaviors of the coligands were discussed in detail
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first three dimensional actinide Polyrotaxane framework mediated by windmill like six connected oligomeric uranyl dual roles of the pseudorotaxane precursor
Dalton Transactions, 2016Co-Authors: Lei Mei, Zhifang Chai, Zhenni Xie, Lin Wang, Liyong Yuan, Wei-qun ShiAbstract:The first 3D actinide Polyrotaxane framework (named IHEP-URCP-2) has been obtained based on windmill-like six-connected high-nuclear oligomeric uranyl nodes under hydrothermal conditions. Notably, the in situ formed pseudorotaxane ligand simultaneously plays dual roles of both a bulky pseudorotaxane linker and a supramolecular guest.
Kazuaki Kato - One of the best experts on this subject based on the ideXlab platform.
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effects of ring size on the dynamics of Polyrotaxane glass
Macromolecules, 2020Co-Authors: Akihiro Ohara, Kazuaki Kato, Koji Michishio, Kohzo ItoAbstract:The dynamics of two Polyrotaxanes with different ring component sizes were compared through viscoelastic measurements. An improved Polyrotaxane synthesis was used to develop a glass-forming polyrot...
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analysis of high molecular weight Polyrotaxanes by maldi tof ms using 3 aminoquinoline based ionic liquid matrix
Journal of the American Society for Mass Spectrometry, 2020Co-Authors: Yuzo Yamazaki, Kazuaki Kato, Shuuichi Nakaya, Kozo ItoAbstract:Polyrotaxane (PR) is a necklace-like supramolecule composed of cyclic components, such as cyclodextrin (CD), and a threading polymer capped with bulky end groups. PR exhibits peculiar mechanical pr...
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one pot synthesis and characterization of Polyrotaxane silica hybrid aerogel
ACS Macro Letters, 2017Co-Authors: Lan Jiang, Hideaki Yokoyama, Kazuaki Kato, Koichi Mayumi, Kohzo ItoAbstract:A novel kind of Polyrotaxane–silica hybrid aerogel is successfully prepared via one-pot sol–gel synthesis in this work. The Polyrotaxane can chemically interpenetrate with Si particles homogeneously in nanoscale, so as to shorten the gelation time and construct a flexible and mechanically strong skeleton. The supramolecular effect ascribable to the sliding motion of cyclic components in Polyrotaxane is introduced into the hybrid aerogel for the first time. Compared with the brittle pure silica aerogel, the obtained Polyrotaxane–silica hybrid aerogels show very low density, low thermal conductivity, and more than two orders magnitude improvement in the compression strength without compromising transparency.
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effect of topological constraint and confined motions on the viscoelasticity of Polyrotaxane glass with different interactions between rings
Journal of Physical Chemistry C, 2017Co-Authors: Kazuaki Kato, Hideaki Yokoyama, Tomoki Mizusawa, Kohzo ItoAbstract:A series of Polyrotaxane glasses composed of poly(ethylene glycol) backbones and threaded α-cyclodextrins (α-CDs) with different substituents were found to exhibit unique viscoelasticities attributed to their interlocked structures, beyond a mere miscible blend of the different components. Differences in the interactions between CDs, which occupied 80 wt % or more of the materials, brought about wide variations in the glass transition temperature and also influenced the cooperativity of segmental motions of the Polyrotaxanes near Tg. These Polyrotaxane melts typically showed negligible cooperativity compared to conventional polymers, behaving as so-called “strong” glass formers. The cooperativity gradually emerged with increasing interaction strength between CDs, and elimination of the threading polymer resulted in “fragile” glass formers. These results suggest that the cooperative motion can be shielded by the topological constraint of the threading polymer, whereas the increasing dominance of convention...
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Effect of Topological Constraint and Confined Motions on the Viscoelasticity of Polyrotaxane Glass with Different Interactions between Rings
2017Co-Authors: Kazuaki Kato, Hideaki Yokoyama, Tomoki Mizusawa, Kohzo ItoAbstract:A series of Polyrotaxane glasses composed of poly(ethylene glycol) backbones and threaded α-cyclodextrins (α-CDs) with different substituents were found to exhibit unique viscoelasticities attributed to their interlocked structures, beyond a mere miscible blend of the different components. Differences in the interactions between CDs, which occupied 80 wt % or more of the materials, brought about wide variations in the glass transition temperature and also influenced the cooperativity of segmental motions of the Polyrotaxanes near Tg. These Polyrotaxane melts typically showed negligible cooperativity compared to conventional polymers, behaving as so-called “strong” glass formers. The cooperativity gradually emerged with increasing interaction strength between CDs, and elimination of the threading polymer resulted in “fragile” glass formers. These results suggest that the cooperative motion can be shielded by the topological constraint of the threading polymer, whereas the increasing dominance of conventional interactions between CDs develops unavoidable cooperativity. Strong secondary relaxation was observed for all of the Polyrotaxane glass samples, and they exhibited considerably higher activation energies than glass made of CD alone. The common secondary relaxation dynamics insensitive to the substituents on the CDs indicate large-scale motion of minor backbone polymers under confinement by similar frozen CD frameworks in the glass state