Co-reporter:Tao Liang and Changle Chen
Organometallics June 26, 2017 Volume 36(Issue 12) pp:2338-2338
Publication Date(Web):June 15, 2017
DOI:10.1021/acs.organomet.7b00294
A series of phosphine-sulfonate ligands bearing various side-arm substituents were designed and prepared. The corresponding Pd(II) complexes [κ2-(P,O)-2-(PPhAr)-1-benzenesulfonato]Pd(Me)(dmso) (Pd1, Ar = o-MeO-C6H4; Pd2, Ar = o-PhO-C6H4; Pd3, Ar = o-(2,6-Me2-C6H3)O-C6H4; Pd4, Ar = o-PhSO2-C6H4) and Ni(II) complexes [κ2-(P,O)-2-(PPhAr)-1-benzenesulfonato]NiPh(PPh3) (Ni1, Ar = o-MeO-C6H4; Ni2, Ar = o-PhO-C6H4; Ni3, Ar = o-(2,6-Me2-C6H3)O-C6H4; Ni4, Ar = o-PhSO2-C6H4) were prepared and applied in ethylene polymerization and ethylene–polar monomer copolymerization. Catalysts Pd2, Pd3, Ni2, and Ni3 are moderately active in ethylene polymerization (activity up to 8.7 × 105 g mol–1 h–1), generating polyethylene with high molecular weights (Mn up to 105100) and high melting temperatures (Tm up to 131.6 °C). The two palladium catalysts can also initiate efficient copolymerization of ethylene with methyl acrylate, allyl cyanide, and allyl acetate. Most importantly, high copolymer molecular weights (Mn between 21600 and 82500) and high polar monomer incorporation ratios (between 6.1% and 15.2%) could be achieved simultaneously in this system. This side-arm strategy is highly effective in modulating the properties of the phosphine-sulfonate palladium and nickel catalysts.
Co-reporter:Kunbo Lian, Yun Zhu, Weimin Li, Shengyu Dai, and Changle Chen
Macromolecules August 22, 2017 Volume 50(Issue 16) pp:6074-6074
Publication Date(Web):August 2, 2017
DOI:10.1021/acs.macromol.7b01087
As a promising alternative to thermoset elastomers, thermoplastic elastomers (TPEs) have attracted much attention because of their unique properties, including processability, reusability and recyclability. The synthesis of TPEs based on olefinic building blocks usually requires the use of long chain α-olefins, multiple steps, and/or multiple catalysts. The concept of using only ethylene as feedstock in a single step is fascinating but also very challenging. In this contribution, we report the synthesis of polyethylene-based TPEs through α-diimine nickel-catalyzed ethylene polymerization. The stress-at-break and strain-at-break values of these polyethylene products could be tuned over a very wide range using different nickel catalysts and different polymerization conditions. Most importantly, products with excellent elastic properties could be generated in the screening process.
Co-reporter:Yinna Na;Dan Zhang
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 15) pp:2405-2409
Publication Date(Web):2017/04/11
DOI:10.1039/C7PY00127D
In this work, ethylene copolymerization and terpolymerization reactions with some nitrogen-containing monomers were investigated using α-diimine palladium and phosphine-sulfonate palladium catalysts. In the α-diimine palladium system, ligand sterics plays an important role and sterically open ligands lead to much better comonomer incorporation. The phosphine-sulfonate palladium catalysts showed much better activities and higher copolymer molecular weights. Copolymers and terpolymers with high molecular weights but significantly different microstructures were obtained in these two systems. The incorporation of polar functionalized comonomers could significantly improve the surface properties of the resulting polymeric products. The water contact angle of pure polyethylene could be reduced from above 100° to ca. 80°. In addition, the mechanical properties of the polyolefins could be modulated by the introduction of these polar monomers.
Co-reporter:Min Li;Xingbao Wang; Yi Luo; Changle Chen
Angewandte Chemie 2017 Volume 129(Issue 38) pp:11762-11767
Publication Date(Web):2017/09/11
DOI:10.1002/ange.201706249
AbstractTransition-metal-catalyzed copolymerization reactions of olefins with polar-functionalized comonomers are highly important and also highly challenging. A second-coordination-sphere strategy was developed to address some of the difficulties encountered in these copolymerization reactions. A series of α-diimine ligands bearing nitrogen-containing second coordination spheres were prepared and characterized. The properties of the corresponding nickel and palladium catalysts in ethylene polymerizations and copolymerizations were investigated. In the nickel system, significant reduction in polymer branching density was observed, while lower polymer branching densities, as well as a wider range of polar monomer substrates, were achieved in the palladium system. Control experiments and computational results reveal the critical role of the metal−nitrogen interaction in these polymerization and copolymerization reactions.
Co-reporter:Dan Zhang; Changle Chen
Angewandte Chemie International Edition 2017 Volume 56(Issue 46) pp:14672-14676
Publication Date(Web):2017/11/13
DOI:10.1002/anie.201708212
AbstractThe transition-metal-catalyzed copolymerization of olefins with polar functionalized co-monomers represents a major challenge in the field of olefin polymerization. It is extremely difficult to simultaneously achieve improvements in catalytic activity, polar monomer incorporation, and copolymer molecular weight through ligand modifications. Herein we introduce a polyethylene glycol unit to some phosphine-sulfonate palladium and nickel catalysts, and its influence on ethylene polymerization and copolymerization is investigated. In ethylene polymerization, this strategy leads to enhanced activity, catalyst stability, and increased polyethylene molecular weight. In ethylene copolymerization with polar monomers, improvements in all copolymerization parameters are realized. This effect is most significant for polar monomers with hydrogen-bond-donating abilities.
Co-reporter:Xiangkai Kong, Hongying Zhu, ChangLe Chen, Guangming Huang, Qianwang Chen
Chemical Physics Letters 2017 Volume 684(Volume 684) pp:
Publication Date(Web):16 September 2017
DOI:10.1016/j.cplett.2017.06.049
•Water molecules not NaBH4 are the hydrogen source for the reduced amino groups.•NaBH4 could contribute to the ionization of H+ from water.•This reduction process is spontaneous to some extent.New insights for the mechanism of nitro to amino groups conversion have been revealed on both N-doped graphene and Ag nanoparticles catalysts, based on the paper assisted ultrasonic spray ionization mass spectrometry: (1) water molecules not NaBH4 are the hydrogen source for the reduced amino groups, (2) NaBH4 could contribute to the ionization of H+ from water, facilitating its adsorption on nitro groups, (3) six different intermediates have been detected to depict the whole catalytic process, and no condensed roots are involved in and (4) this reduction process is spontaneous to some extent, and even without catalysts it is not totally stopped as obtained from the spectral measurements.Download high-res image (38KB)Download full-size image
Co-reporter:Bangpei Yang;Shuoyan Xiong
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 40) pp:6272-6276
Publication Date(Web):2017/10/17
DOI:10.1039/C7PY01281K
Phosphine-sulfonate-based Pd and Ni complexes are widely recognized as potent catalysts for ethylene polymerization and copolymerizations with polar functionalized comonomers. Significant efforts have been directed towards modifying ligand structures and improving catalyst properties. In this contribution, we install a heterocyclic unit in the phosphine-sulfonate ligand framework and study the properties of their corresponding Pd and Ni catalysts. The furyl- and benzofuryl-derived phosphine-sulfonate palladium catalysts show high activities for ethylene polymerization and copolymerization with polar monomers (methyl acrylate, butyl acrylate, 6-chloro-1-hexene, 10-undecenol, and 10-hendecenoic acid). The furyl- and benzofuryl-derived phosphine-sulfonate nickel catalysts are also highly active for ethylene polymerization. The N-methylpyrrolyl-, thienyl-, and benzothienyl-derived palladium and nickel catalysts demonstrate very low or no activity in ethylene polymerization. The microstructures of the resulting polyethylene (highly linear vs. highly branched) are significantly affected by the nature of the heterocyclic substituent. Interactions between the heteroatoms and the metal centers, as well as the π–π stacking between the heterocyclic unit and the benzo backbone in the ligand are hypothesized to play important roles in determining the properties of these metal catalysts.
Co-reporter:Guangzhi Song;Wenmin Pang;Weimin Li;Min Chen
Polymer Chemistry (2010-Present) 2017 vol. 8(Issue 47) pp:7400-7405
Publication Date(Web):2017/12/06
DOI:10.1039/C7PY01661A
In this contribution, the effect of substitution on biaryl-based phosphine-sulfonate nickel catalysts is investigated. A series of [κ2-(P,O)-2-(P-PhAr)-1-benzenesulfonato]NiPh(PPh3) nickel complexes (Ni–OMe, Ar = 2-[2′,6′-(OMe)2-C6H3]-C6H4; Ni–H, Ar = 2-(C6H5)-C6H4; Ni–OiPr, Ar = 2-[2′,6′-(OiPr)2-C6H3]-C6H4; Ni–F, Ar = 2-[2′,6′-F2-C6H3]-C6H4) are prepared and applied to the polymerization of ethylene as well as its copolymerizations with polar functionalized norbornene comonomers. These nickel complexes are highly active toward ethylene polymerization without the requirement of any cocatalyst. Specifically, the Ni–F complex exhibits high stability and high activity (up to 3.0 × 106 g mol−1 h−1), and catalyzes the formation of polyethylene of high molecular weight (Mn up to 216 200) and high melting point (Tm up to 139.6 °C). The polyethylene molecular-weight distribution from this system is very sensitive to the steric demand of the ligand, as well as the nature of the coordinating base, polymerization temperature, and ethylene pressure. This, in turn, provides a simple and efficient strategy for the control of the polyethylene molecular-weight distribution, which is an important parameter that determines multiple material properties such as viscosity, stiffness, and crystallinity. Ni–F also exhibits good ethylene-copolymerization behavior toward polar-functionalized norbornene comonomers, leading to moderate comonomer incorporation in copolymers of moderate molecular weight and high melting point.
Co-reporter:Xuelin Sui;Changwen Hong;Wenmin Pang
Materials Chemistry Frontiers 2017 vol. 1(Issue 5) pp:967-972
Publication Date(Web):2017/05/04
DOI:10.1039/C6QM00235H
Previously, it was demonstrated that nickel complexes bearing unsymmetrical α-diimine ligands generated polymers with a broad molecular weight distribution in ethylene polymerization. In this contribution, the influence of some unsymmetrical α-diimine ligands on the catalytic properties of their palladium complexes was investigated in ethylene polymerization, ethylene–methyl acrylate copolymerization and 1-hexene polymerization. Quite interestingly, the unsymmetrical α-diimine ligand structures did not lead to a broad molecular weight distribution in these polymerization and copolymerization reactions. In addition, the influence of different substituents (OMe, Me, Cl and NO2) and different backbone structures was studied. The palladium complexes bearing electron-donating groups showed higher thermal stability and afforded polymers with a much higher molecular weight. The palladium complex bearing naphthalene backbone showed a much lower catalytic activity, generating polymers or copolymers with a much lower molecular weight. The mechanical and surface properties of the resulting polymer and copolymer were also investigated.
Co-reporter:Lihua Guo;Wenjing Liu
Materials Chemistry Frontiers 2017 vol. 1(Issue 12) pp:2487-2494
Publication Date(Web):2017/11/22
DOI:10.1039/C7QM00321H
In this review, recent developments on late transition metal catalyzed α-olefin polymerization and copolymerization with polar comonomers are described. First, the polymerization mechanisms of early and late transition metal catalyzed α-olefin polymerization are compared. Second, cationic catalysts bearing α-diimine and related ligands as well as neutral catalysts bearing anionic ligands for α-olefin homopolymerization are discussed in detail. Third, late transition metal catalyzed α-olefin copolymerization with polar functionalized comonomers is summarized. Special attention is paid to the regio- and stereo-selectivity induced by late transition metal catalysts in these polymerization and copolymerization reactions.
Co-reporter:Wenping Zou;Wenmin Pang
Inorganic Chemistry Frontiers 2017 vol. 4(Issue 5) pp:795-800
Publication Date(Web):2017/05/16
DOI:10.1039/C6QI00562D
Two palladium complexes (NHC)Pd(allyl)Cl (NHC = 1,3-Ar2-naphthoquinimidazolylidene, Ar = 2,6-Me2-C6H3, 2,6-iPr2-C6H3) bearing a redox-active naphthoquinone moiety, were prepared and characterized. Electro-chemistry cyclic voltammetry and NMR studies showed that these palladium complexes could be easily reduced and re-oxidized using CoCp2 and [FeCp2][BAF] (BAF = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) reagents. The properties of these neutral and reduced palladium complexes in norbornene, 5-norbornene-2-yl acetate and 1-chloro-1-octyne polymerization were studied. The neutral complexes were active in all of these polymerization reactions in the presence of Na[BAF]. In contrast, the reduced analogues showed very low activity under the same conditions. As such, switchable polymerization could be realized in this catalytic system.
Co-reporter:Lihua Guo, Shengyu Dai, Xuelin Sui, and Changle Chen
ACS Catalysis 2016 Volume 6(Issue 1) pp:428
Publication Date(Web):December 7, 2015
DOI:10.1021/acscatal.5b02426
In this perspective, recent developments on palladium and nickel mediated chain walking olefin polymerization and copolymerization with polar functionalized comonomers are described. First, the chain walking polymerization mechanism is discussed followed by its implications in olefin polymerization and copolymerization. Then, recent advances in catalyst design are provided. Special attention is paid to the influence of ligand structures on the catalytic properties. Subsequently, the applications of these chain walking polymerization catalysts in the synthesis of functionalized hyperbranched polymers and copolymers are summarized. Finally, some recent developments and perspectives on very fast and very slow chain walking polymerization catalysts are discussed.Keywords: chain walking; copolymerization; functionalized polyethylene; nickel catalysts; olefin polymerization; palladium catalysts; polar monomer
Co-reporter:Ruikun Wang, Minhui Zhao and Changle Chen
Polymer Chemistry 2016 vol. 7(Issue 23) pp:3933-3938
Publication Date(Web):05 May 2016
DOI:10.1039/C6PY00750C
A series of α-diimine ligands and their corresponding palladium complexes were synthesized and characterized. These α-diimine ligands possess unique properties, which could lead to metal complexes with very similar electronic and steric environments around a palladium center. For example, the CO stretching frequencies of the palladium carbonyl complexes are very similar. At a remote position on the second coordination sphere of the ligand structure, substituents (Ph, CF3, NO2 and OMe) are installed to probe their potential influences on olefin polymerization and copolymerization processes. The properties of these palladium complexes in ethylene polymerization, ethylene/methyl acrylate copolymerization, ethylene/norbornene copolymerization and ethylene/5-norbornene-2-yl acetate copolymerization are investigated in detail. Interestingly, most of the metal complexes behaved very similarly to each other except for the complex bearing a Ph substituent, which showed much better activity and generated polymers with much higher molecular weight.
Co-reporter:Xiaohui Hu, Shengyu Dai and Changle Chen
Dalton Transactions 2016 vol. 45(Issue 4) pp:1496-1503
Publication Date(Web):07 Dec 2015
DOI:10.1039/C5DT04408A
The synthesis, characterization and ethylene polymerization properties of a series of salicylaldimine Ni(II) complexes with a dibenzhydryl moiety are described. These Ni complexes are designed to bear systematically varied electron donating and withdrawing substituents. These complexes are among the most active salicylaldimine Ni(II) catalysts in ethylene polymerization. Moreover, these complexes demonstrate good thermal stability, maintaining high activity at 80 °C. The polyethylene generated possesses a high molecular weight, moderate branching density and high melting temperature. Surprisingly, the electronic perturbations only exert moderate influence on the ethylene polymerization process despite the covalently close proximity of the electron donating or withdrawing substituents to the metal center. Comparing with the traditional iso-propyl substituted nickel analogue, these new complexes show up to an order of magnitude higher activity, generating polyethylene with much higher molecular weight, similar or slightly lower branching density and much higher melting temperature.
Co-reporter:Wenping Zou and Changle Chen
Organometallics 2016 Volume 35(Issue 11) pp:1794-1801
Publication Date(Web):May 18, 2016
DOI:10.1021/acs.organomet.6b00202
A series of α-diimine ligands with different substituents on the acenaphthyl backbone were synthesized and characterized. The corresponding Ni(II) and Pd(II) complexes were prepared and used in ethylene polymerization and copolymerization with methyl acrylate. In ethylene polymerization, these Ni(II) complexes showed activities of up to 1.6 × 107 g/((mol of Ni) h), generating polyethylene with a molecular weight (Mn) of up to 4.2 × 105. Interestingly, these Ni(II) complexes behave very similarly in ethylene polymerization except for the complex with two methoxy substituents on the ortho position of the acenaphthyl backbone, in which case about 3 times higher polyethylene molecular weight and much lower branching density were observed. The ligand substituent effect is much more dramatic for the Pd(II) complexes. In ethylene polymerization, activities of up to 1.7 × 105 g/((mol of Pd) h) and a polyethylene molecular weight (Mn) of up to 4.7 × 104 could be obtained. The Pd(II) complex with two methoxy substituents on the ortho position of the acenaphthyl backbone demonstrated much higher activity and generated polyethylene with about 3 times higher molecular weight than that for the classic Pd(II) complex. A similar trend was maintained in ethylene–methyl acrylate copolymerization.
Co-reporter:Zixia Wu, Min Chen, and Changle Chen
Organometallics 2016 Volume 35(Issue 10) pp:1472-1479
Publication Date(Web):March 16, 2016
DOI:10.1021/acs.organomet.6b00076
A series of naphthalene-bridged phosphine–sulfonate ligands and the corresponding Pd(II) complexes [κ2(P,O)-2-(R2P)-1-naphthalenesulfonato]Pd(Me)(dmso) (1, R = Ph; 2, R = o-MeO-C6H4; 3, R = Cy) and Ni(II) complexes [κ2(P,O)-2-(R2P)-1-naphthalenesulfonato]Ni(η3-C3H5) (Ni-1, R = o-MeO-C6H4; Ni-2, R = Cy) have been prepared and characterized. The analogous benzo-bridged phosphine–sulfonate Pd(II) complex [κ2(P,O)-(R2P)-benzenesulfonato]Pd(Me)(dmso) (2′, R = o-MeO-C6H4) and Ni(II) complex [κ2(P,O)-(R2P)-benzenesulfonato]Ni(η3-C3H5) (Ni-1′, R = o-MeO-C6H4) were prepared for comparison. In ethylene polymerization, complex 2 showed activity of up to 7.5 × 106 g mol–1 h–1, which is among the most active palladium catalysts for ethylene homopolymerization. Under the same conditions, complex 2 showed up to 1 order of magnitude higher catalytic activity than complex 2′, generating polyethylene with slightly smaller molecular weight and similar branching density. The Ni(II) complex Ni-1 was also more active than complex Ni-1′, generating polyethylene with up to 1 order of magnitude higher molecular weight. In ethylene–methyl acrylate copolymerization, complex 2 showed lower activity, affording a copolymer with higher methyl acrylate incorporation and higher copolymer molecular weight in comparison to complex 2′.
Co-reporter:Ruikun Wang;Xuelin Sui;Wenmin Pang;Dr. Changle Chen
ChemCatChem 2016 Volume 8( Issue 2) pp:434-440
Publication Date(Web):
DOI:10.1002/cctc.201501041
Abstract
The synthesis, characterization, and ethylene polymerization properties of a series of xanthene-bridged dinuclear α-diimine NiII complexes are described. The dinucleating α-diimine ligands were prepared from the xanthene-bridged di-anilines, which were synthesized and isolated on the multigram scale without using column chromatography. The di-anilines could potentially be used to prepare various dinucleating imine-containing olefin polymerization ligands. In ethylene polymerization, the dinuclear α-diimine NiII complexes showed good thermal stability and high catalytic activity. In addition, the polyethylene generated by these dinuclear α-diimine NiII complexes showed high molecular weight, narrow polydispersity, and very low branching density. Metal–metal cooperativity effects was invoked to explain the slow β-hydride elimination process and the correspondingly slow chain-walking process.
Co-reporter:Shengyu Dai, Shixin Zhou, Wen Zhang, and Changle Chen
Macromolecules 2016 Volume 49(Issue 23) pp:8855-8862
Publication Date(Web):November 29, 2016
DOI:10.1021/acs.macromol.6b02104
In the Brookhart type α-diimine palladium catalyst system, it is highly challenging to tune the polymer branching densities through ligand modifications or polymerization conditions. In this contribution, we describe the synthesis and characterization of a series of α-diimine ligands and the corresponding palladium catalysts bearing both the dibenzhydryl moiety and with systematically varied ligand sterics. In ethylene polymerization, it is possible to tune the catalytic activities ((0.77–8.85) × 105 g/(mol Pd·h)), polymer molecular weights (Mn: (0.2–164.7) × 104), branching densities (25–116/1000C), and polymer melting temperatures (amorphous to 98 °C) over a very wide range. In ethylene–methyl acrylate (E–MA) copolymerization, it is possible to tune the catalytic activities ((0.3–8.8) × 103 g/(mol Pd·h)), copolymer molecular weights (1.1 × 103–79.8 × 103), branching densities (30–119/1000C), and MA incorporation ratio (0.4–13.8%) over a very wide range. The molecular weights and branching densities could also be tuned in α-olefin polymerization. The tuning in polymer microstructures leads to significant tuning in polyethylene mechanical properties and the surface properties of the E–MA copolymer.
Co-reporter:Xuelin Sui, Shengyu Dai, and Changle Chen
ACS Catalysis 2015 Volume 5(Issue 10) pp:5932
Publication Date(Web):September 1, 2015
DOI:10.1021/acscatal.5b01490
The synthesis, characterization, and olefin (co)polymerization studies of a series of palladium complexes bearing phosphine phosphonic amide ligands were investigated. In this ligand framework, substituents on three positions could be modulated independently, which distinguishes this class of ligand and provides a great deal of flexibilities and opportunities to tune the catalytic properties. The palladium complex with an o-MeO-Ph substituent on phosphine is one of the most active palladium catalysts in ethylene polymerization, with 1 order of magnitude higher activity than the corresponding classic phosphine-sulfonate palladium complex. Meanwhile, the polyethylene generated by this new palladium complex showed ca. 6 times higher molecular weight in comparison to that by the classic phosphine-sulfonate palladium complex. In ethylene/methyl acrylate copolymerization, the new palladium complex showed lower activity, generating copolymer with similar methyl acrylate incorporation and much higher molecular weight. The new palladium complex was also able to copolymerize ethylene with other polar monomers, including butyl vinyl ether and allyl acetate, making it one of the very few catalyst systems that can copolymerize ethylene with multiple industrially relevant polar monomers.Keywords: copolymerization; olefin polymerization; palladium; phosphine ligands; polar monomer
Co-reporter:Min Li and Changle Chen
Polymer Chemistry 2015 vol. 6(Issue 40) pp:7127-7132
Publication Date(Web):25 Aug 2015
DOI:10.1039/C5PY01067E
The combination of N-heterocyclic carbene-ligated Pd complexes with sodium tetrakis(3,5-bis(trifluoromethyl)phenyl)borate bearing highly weakly coordinating anions led to the formation of highly active catalysts for the polymerization of disubstituted acetylenes. The use of both carbene ligands and the weakly coordinating anions was critical to obtain high activity and great control over the polymerization process. The Pd-generated polymers showed higher molecular weight, lower solubility and higher thermal stability than the Mo-based polymers. The molecular weight of the resulting polymers can be efficiently modulated by the addition of α-olefin, which acted as a chain transfer agent in this system.
Co-reporter:Min Chen, Wenping Zou, Zhengguo Cai and Changle Chen
Polymer Chemistry 2015 vol. 6(Issue 14) pp:2669-2676
Publication Date(Web):05 Feb 2015
DOI:10.1039/C5PY00010F
A series of phosphine-sulfonate nickel and palladium complexes [(o-R2-PC6H4SO3)M(allyl)] (1a, R = Ph, M = Ni; 1b, R = o-MeO-C6H4, M = Ni; 1c, R = Cy, M = Ni, 2, R = Cy, M = Pd) were synthesized and characterized. The reaction of B(C6F5)3 with complex 1c led to the isolation of complex [(o-Cy2-PC6H4SO3·B(C6F5)3)Ni(allyl)] (3c). In the X-ray structure of 3c, the binding of B(C6F5)3 to a sulfonate oxygen was observed. The X-ray analysis also suggests a zwitterionic resonance structure of 3c. In norbornene homopolymerization, 1a–1c showed very low activity. The addition of B(C6F5)3 to the system led to an up to 4000 fold increase in the catalytic activity. Under optimized conditions, an activity of up to 1.2 × 107 g mol−1 h−1 was observed for the B(C6F5)3 adduct of 1c. Interestingly, the palladium analogue 2 was not active at all with or without the addition of B(C6F5)3 under the same conditions. In ethylene homopolymerization, the addition of B(C6F5)3 led to an increase in the activity and a decrease in the molecular weight, which is probably due to the reduction of electron density from the nickel center upon B(C6F5)3 binding. In ethylene-norbornene copolymerization, complex 1c showed good activity with up to 10.1% of norbornene incorporation. Interestingly, a decrease in the activity was observed with the addition of B(C6F5)3.
Co-reporter:Min Chen;Bangpei Yang ; Changle Chen
Angewandte Chemie 2015 Volume 127( Issue 51) pp:15740-15744
Publication Date(Web):
DOI:10.1002/ange.201507274
Abstract
The facile and reversible interconversion between neutral and oxidized forms of palladium complexes containing ferrocene-bridged phosphine sulfonate ligands was demonstrated. The activity of these palladium complexes could be controlled using redox reagents during ethylene homopolymerization, ethylene/methyl acrylate copolymerization, and norbornene oligomerization. Specifically in norbornene oligomerization, the neutral complexes were not active at all whereas the oxidized counterparts showed appreciable activity. In situ switching between the neutral and oxidized forms resulted in an interesting “off” and “on” behavior in norbornene oligomerization. This work provides a new strategy to control the olefin polymerization process.
Co-reporter:Lihua Guo
Science China Chemistry 2015 Volume 58( Issue 11) pp:1663-1673
Publication Date(Web):2015 November
DOI:10.1007/s11426-015-5433-7
In this review, a recent development of cationic α-diimine palladium(II) complexes for ethylene polymerization and copolymerization with polar functionalized comonomers was briefly described. First, the polymerization mechanism for this type of catalysts was discussed. Next, recent advances in ligand design were provided with special focus on the influence of ligand structures on the catalytic polymerization properties. Last, the ethylene homopolymerization and copolymerization with various polar comonomers, especially acrylate and vinyl ethers were summarized.
Co-reporter:Min Li, Min Chen, Changle Chen
Polymer 2015 Volume 64() pp:234-239
Publication Date(Web):1 May 2015
DOI:10.1016/j.polymer.2014.11.060
•A series of anilinotropone-based aluminum complexes were synthesized.•They are highly active in the ring-opening polymerization of rac-lactide.•Small aluminum chelate ring may contribute to the high activity.•Side-arm strongly affects the catalytic properties of the catalysts.A series of anilinotropone-based aluminum complexes of general formula (Ar-NC7H5O)AlMe2 (1, Ar = Ph; 2, Ar = 2,6-iPrC6H3; 3, Ar = (2-O-Ph)C6H4; 4, Ar = (2-O-2,6-iPr2-Ph)C6H4; 5, Ar = (2-S-Ph)C6H4) were synthesized at high yields. These complexes were characterized by 1H, 13C NMR spectroscopy, elemental analysis and mass spectroscopy. X-ray analysis of complexes 1, 3 and 5 showed that they exist as dimeric species in solid state and the Al center adopts a distorted trigonal-bipyramidal geometry. Complexes 1–5 are highly active in the ring-opening polymerization (ROP) of rac-lactide (rac-LA) in the presence of benzyl alcohol as an initiator. Sidearm on the ligand has a dramatic effect on the catalysis, and complexes 3–5 bearing heteroatom containing sidearm are much more active than complexes 1 and 2. Especially, near complete consumption of the monomer was observed for complex 3 at rac-LA/Al ratio of 100 and 80 °C, representing one of the most active aluminum catalysts for ROP of rac-LA. The smaller aluminum chelate ring size and the resulting bigger ring tension may contribute to the high activity. In addition to the catalytic activity, the isotacticity of the resulting polylactide is also affected by the sidearm.
Co-reporter:Shengyu Dai;Xuelin Sui ; Changle Chen
Angewandte Chemie International Edition 2015 Volume 54( Issue 34) pp:9948-9953
Publication Date(Web):
DOI:10.1002/anie.201503708
Abstract
A series of sterically demanding α-diimine ligands bearing electron-donating and electron-withdrawing substituents were synthesized by an improved synthetic procedure in high yield. Subsequently, the corresponding Pd complexes were prepared and isolated by column chromatography. These Pd complexes demonstrated unique properties in ethylene polymerization, including high thermal stability and high activity, thus generating polyethylene with a high molecular weight and very low branching density. Similar properties were observed for ethylene/methyl acrylate copolymerization. Because of the high molecular weight and low branching density, the generated polyethylene and ethylene/methyl acrylate copolymer were semicrystalline solids. The (co)polymers had unique microstructures originating from the unique slow-chain-walking activity of these Pd complexes.
Co-reporter:Min Chen;Bangpei Yang ; Changle Chen
Angewandte Chemie International Edition 2015 Volume 54( Issue 51) pp:15520-15524
Publication Date(Web):
DOI:10.1002/anie.201507274
Abstract
The facile and reversible interconversion between neutral and oxidized forms of palladium complexes containing ferrocene-bridged phosphine sulfonate ligands was demonstrated. The activity of these palladium complexes could be controlled using redox reagents during ethylene homopolymerization, ethylene/methyl acrylate copolymerization, and norbornene oligomerization. Specifically in norbornene oligomerization, the neutral complexes were not active at all whereas the oxidized counterparts showed appreciable activity. In situ switching between the neutral and oxidized forms resulted in an interesting “off” and “on” behavior in norbornene oligomerization. This work provides a new strategy to control the olefin polymerization process.
Co-reporter:Shengyu Dai;Xuelin Sui ; Changle Chen
Angewandte Chemie 2015 Volume 127( Issue 34) pp:10086-10091
Publication Date(Web):
DOI:10.1002/ange.201503708
Abstract
A series of sterically demanding α-diimine ligands bearing electron-donating and electron-withdrawing substituents were synthesized by an improved synthetic procedure in high yield. Subsequently, the corresponding Pd complexes were prepared and isolated by column chromatography. These Pd complexes demonstrated unique properties in ethylene polymerization, including high thermal stability and high activity, thus generating polyethylene with a high molecular weight and very low branching density. Similar properties were observed for ethylene/methyl acrylate copolymerization. Because of the high molecular weight and low branching density, the generated polyethylene and ethylene/methyl acrylate copolymer were semicrystalline solids. The (co)polymers had unique microstructures originating from the unique slow-chain-walking activity of these Pd complexes.
Co-reporter:Xiang-Kai Kong, Chang-Le Chen and Qian-Wang Chen
Chemical Society Reviews 2014 vol. 43(Issue 8) pp:2841-2857
Publication Date(Web):06 Feb 2014
DOI:10.1039/C3CS60401B
Graphene has attracted increasing attention in different scientific fields including catalysis. Via modification with foreign metal-free elements such as nitrogen, its unique electronic and spin structure can be changed and these doped graphene sheets have been successfully employed in some catalytic reactions recently, showing them to be promising catalysts for a wide range of reactions. In this review, we summarize the recent advancements of these new and interesting catalysts, with an emphasis on the universal origin of their catalytic mechanisms. We are full of hope for future developments, such as more precisely controlled doping methods, atom-scale surface characterization technology, generating more active catalysts via doping, and finding wide applications in many different fields.
Co-reporter:Haibo Hu, Hao Zhong, Changle Chen and Qianwang Chen
Journal of Materials Chemistry A 2014 vol. 2(Issue 19) pp:3695-3702
Publication Date(Web):20 Jan 2014
DOI:10.1039/C3TC32228A
A high performance photonic anti-counterfeiting watermark that can be incorporated into banknotes has been developed by combining a novel invisible photonic printing with a flexible, translucent and ultra-thin magnetic-responsive photonic display film. The photonic anti-counterfeiting watermark has latent colourful patterns that are lithographically printable and magnetically responsive, and can be easily perceived by the naked eye under magnetic fields. In addition, the distinct differences of the spectral characteristics between the invisible-form and the visible-form of the patterns can be accurately detected by using a special optical instrument, which makes the photonic anti-counterfeiting watermark provide double security information to identify the authenticity of banknotes. Moreover, the strategy allows accurate control of the optical diffraction colour and the structural design of the latent patterns. The fabrication process does not damage the banknotes and allows fast, convenient and scalable production at low-costs. The present work demonstrates that the fabrication of high performance photonic-crystal-based anti-counterfeiting devices on banknotes is possible.
Co-reporter:Zhengsong Lou, Minglong He, Ruikun Wang, Weiwei Qin, Dejian Zhao, and Changle Chen
Inorganic Chemistry 2014 Volume 53(Issue 4) pp:2053-2057
Publication Date(Web):January 31, 2014
DOI:10.1021/ic402558t
Sub-micrometer-sized magnesium ferrite spheres consisting of uniform small particles have been prepared using a facile, large-scale solid-state reaction employing a molten salt technique. Extensive structural characterization of the as-prepared samples has been performed using scanning electron microscope, transmission electron microscopy, high-resolution transmission electron microscopy, selected area electron diffraction, and X-ray diffraction. The yield of the magnesium ferrite sub-micrometer spheres is up to 90%, and these sub-micrometer spheres are made up of square and rectangular nanosheets. The magnetic properties of magnesium ferrite sub-micrometer spheres are investigated, and the magnetization saturation value is about 24.96 emu/g. Moreover, the possible growth mechanism is proposed based on the experimental results.
Co-reporter:Xuepeng Zhang;Minxin Cui;Rui Zhou;Guoqing Zhang
Macromolecular Rapid Communications 2014 Volume 35( Issue 5) pp:566-573
Publication Date(Web):
DOI:10.1002/marc.201300834
Co-reporter:Lei Gao, Haibo Hu, Xuelin Sui, Changle Chen, and Qianwang Chen
Environmental Science & Technology 2014 Volume 48(Issue 11) pp:6500-6507
Publication Date(Web):April 25, 2014
DOI:10.1021/es5006708
Pyrolysis of 1 g of waste chicken feathers (quills and barbs) in supercritical carbon dioxide (sc-CO2) system at 600 °C for 3 h leads to the formation of 0.25 g well-shaped carbon microspheres with diameters of 1–5 μm and 0.26 g ammonium bicarbonate ((NH4)HCO3). The products were characterized by powder X-ray diffraction (XRD), Field emission scanning electron microscopy (FE-SEM), Raman spectroscopic, FT-IR spectrum, X-ray electron spectroscopy (XPS), and N2 adsorption/desorption measurements. The obtained carbon microspheres displayed great superhydrophobicity as fabric coatings materials, with the water contact angle of up to 165.2 ± 2.5°. The strategy is simple, efficient, does not require any toxic chemicals or catalysts, and generates two valuable materials at the same time. Moreover, other nitrogen-containing materials (such as nylon and amino acids) can also be converted to carbon microspheres and (NH4)HCO3 in the sc-CO2 system. This provides a simple strategy to extract the nitrogen content from natural and man-made waste materials and generate (NH4)HCO3 as fertilizer.
Co-reporter:Lei Gao, Ran Li, Xuelin Sui, Ren Li, Changle Chen, and Qianwang Chen
Environmental Science & Technology 2014 Volume 48(Issue 17) pp:10191-10197
Publication Date(Web):August 4, 2014
DOI:10.1021/es5021839
Poultry feather is renewable, inexpensive and abundantly available. It holds great business potentials if poultry feather can be converted into valuable functional materials. Herein, we describe a strategy for the catalytic conversion of chicken feather waste to Ni3S2-carbon coaxial nanofibers (Ni3S2@C) which can be further converted to nitrogen doped carbon nanotubes (N-CNTs). Both Ni3S2@C and N-CNTs exhibit high catalytic activity and good reusability in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 with a first-order rate constant (k) of 0.9 × 10–3 s–1 and 2.1 × 10–3 s–1, respectively. The catalytic activity of N-CNTs is better than that of N-doped graphene and comparable to commonly used noble metal catalysts. The N content in N-CNTs reaches as high as 6.43%, which is responsible for the excellent catalytic performance. This strategy provides an efficient and low-cost method for the comprehensive utilization of chicken feathers. Moreover, this study provides a new direction for the application of N-CNTs.
Co-reporter:Haibo Hu, Lei Gao, Changle Chen, and Qianwang Chen
Environmental Science & Technology 2014 Volume 48(Issue 5) pp:2928-2933
Publication Date(Web):February 6, 2014
DOI:10.1021/es404345b
Onionlike carbon microspheres composed of many nanoflakes have been prepared by pyrolyzing waste polyethylene terephthalate in supercritical carbon dioxide at 650 °C for 3 h followed by subsequent vacuum annealing at 1500 °C for 0.5 h. The obtained onionlike carbon microspheres have very high surface roughness and exhibit unique hydrophobic properties. Considering their structural similarities with a lotus leaf, we further developed a low-cost, acid/alkaline-resistant, and fluorine-free superhydrophobic coating strategy on fabrics by employing the onionlike carbon microspheres and polydimethylsiloxane as raw materials. This provides a novel technique to convert waste polyethylene terephthalate to valuable carbon materials. At the same time, we demonstrate a novel application direction of carbon materials by taking advantage of their unique structural properties. The combination of recycling waste solid materials as carbon feedstock for valuable carbon material production, with the generation of highly value-added products such as superhydrophobic fabrics, may provide a feasible solution for sustainable solid waste treatment.
Co-reporter:Liang Zhu, Zhi-Sheng Fu, Hui-Jie Pan, Wei Feng, Changle Chen and Zhi-Qiang Fan
Dalton Transactions 2014 vol. 43(Issue 7) pp:2900-2906
Publication Date(Web):21 Nov 2013
DOI:10.1039/C3DT51782A
A series of binuclear nickel/palladium catalysts C4–C7 with conjugated α-diimine ligands were designed, prepared and fully characterized. The binuclear nickel complexes C6 and C7 were activated by modified methylalumoxanes (MMAO) to generate highly active ethylene polymerization catalysts with activities up to 1050 kg [mol (Ni) h]−1. The activity of C7 is twice that of the mononuclear analogue under the same conditions. The effects of the catalyst structure, cocatalyst ratio, polymerization time, solvent and feeding monomer on the catalytic activities, molecular weight and branching structures of the resulting polymers were evaluated. The binuclear palladium complexes C4–C5 produced polyethylene with two separate peaks in GPC curves in ethylene polymerization. In contrast, the mononuclear analogue C3 produces polyethylene with a unimodal GPC curve. Probably, two active species are generated in the binuclear palladium catalyst system and are responsible for the bimodal feature of the GPC curves. The performance of the binuclear palladium complexes in ethylene/methyl acrylate copolymerization was also investigated.
Co-reporter:Yang Li, Wenjian Wu, Peng Dai, Lili Zhang, Zhaoqi Sun, Guang Li, Mingzai Wu, Xiaoshuang Chen and Changle Chen
RSC Advances 2014 vol. 4(Issue 45) pp:23831-23837
Publication Date(Web):19 May 2014
DOI:10.1039/C4RA02161D
In this paper, TiO2 nanowires decorated with WO3 nanoparticles (WO3-TWS) on Ti foils were prepared using simple hydrothermal treatment, wet impregnation and subsequent annealing treatment, sequentially. Ag nanoparticles were successfully deposited on the obtained WO3-TWS by a successive ionic layer adsorption reaction technique. Ultraviolet-visible absorption spectra showed that the introduction of Ag and WO3 particles on TiO2 nanowire surfaces extends the absorption edge to the visible light regime. More importantly, the increase of Ag content greatly enhances the absorption intensity in the visible light regime. The photocatalytic experiment results revealed that TiO2 nanowires decorated with Ag and WO3 nanoparticles possess higher photocatalytic activities toward methyl orange than pure TiO2 nanowires. The degradation percentage of 95.6% after 10 cycles indicated that the as-prepared photocatalyst composites exhibited excellent long-time recyclability for the degradation of contaminants.
Co-reporter:Xiaoyan Wang, Yongxia Wang, Xincui Shi, Jingyu Liu, Changle Chen, and Yuesheng Li
Macromolecules 2014 Volume 47(Issue 2) pp:552-559
Publication Date(Web):January 9, 2014
DOI:10.1021/ma4022696
Catalyzed by the (pyridylamido)hafnium/organoboron system, a series of halogen-functionalized isotactic polypropylenes were synthesized via the stereospecific copolymerization of propylene with ω-halo-α-alkenes. The (pyridylamido)hafnium/organoboron system has been proved to be a potent catalyst for propylene/ω-iodo-α-alkenes copolymerization, producing well-defined poly(propylene-co-ω-iodo-α-undecene)s with outstanding properties. The high molecular weight (Mw > 100 kg mol–1) functional iPPs possessing abundant iodoalkene units (up to 11.7 mol %) and unimodal molecular weight distributions (Mw/Mn ≈ 2) could be easily obtained under mild conditions with excellent catalytic activity. High isotactic selectivity of monomers, including propylene and polar comonomer, was unexpectedly observed ([mmmm] > 99%). Moreover, based on the unique copolymerization process and the highly reactive sites on the copolymers, the halogen groups of the resultant copolymers could be easily transformed into other polar groups via click chemistry, and the new functional iPPs with high molecular weights and abundant polar groups could be efficiently obtained.
Co-reporter:Yanlu Zhang, Yanchun Cao, Xuebing Leng, Changle Chen, and Zheng Huang
Organometallics 2014 Volume 33(Issue 14) pp:3738-3745
Publication Date(Web):July 16, 2014
DOI:10.1021/om5004094
A series of cationic palladium(II) complexes bearing phosphine–sulfonamide ligands, [(P,O)PdMe(lutidine)][SbF6], were synthesized and used for catalytic ethylene oligomerization. The molecular structure of the complex {[N,N-dicyclohexyl-2-(diphenylphosphanyl)benzenesulfonamide]PdMe(lutidine)}[SbF6] shows that the phosphorus atom and the oxygen atom coordinate to the palladium center. The ethylene oligomerization behavior is greatly influenced by the phosphino substituents, while the substituents on sulfonamide show only minimal effects. Complexes containing the diphenylphosphanyl group are highly selective for ethylene dimerization, affording 1-butene exclusively with moderate activity. The bulkier bis(2-methoxyphenyl)phosphanyl group leads to higher activity and gives α-olefins containing mainly 1-butene and 1-hexene, with a 1-hexene content of up to 35%. The palladium complexes bearing alkyl phosphino substituents give 1-butene and 1-hexene as the major products; a small amount of 2-butene (<5%) was observed, suggesting the occurrence of chain walking. The addition of B(C6F5)3 greatly enhances the catalytic activity. Experimental results suggest that the increase in activity is likely due to the abstraction of lutidine, not from the coordination of B(C6F5)3 to the sulfonamide oxygen atom.
Co-reporter:Haibo Hu, Changle Chen and Qianwang Chen
Journal of Materials Chemistry A 2013 vol. 1(Issue 38) pp:6013-6030
Publication Date(Web):20 May 2013
DOI:10.1039/C3TC30657G
Magnetically induced self-assembly is a very powerful method that can quickly, efficiently and reversibly assemble magnetic colloidal particles into ordered structures with tunable photonic properties. The recent developments in the techniques have enabled convenient modulation of photonic properties and easy fabrication of sophisticated photonic structures. As a result, various practical applications such as magnetically controlled display units, photonic humidity sensors, reusable photonic paper/ink, photonic anti-counterfeiting, high resolution full-color photonic printing and invisible photonic printing have been demonstrated. In this feature article, we will describe these recent advances, with special focus on magnetically induced self-assembly of colloidal particles into 1D chainlike photonic structures, and discuss the emerging applications of this new technique.
Co-reporter:Ren Li, Peng Zhang, Yimin Huang, Changle Chen, and Qianwang Chen
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 23) pp:12695
Publication Date(Web):November 21, 2013
DOI:10.1021/am4040762
The separation and reuse of nanocatalysts remains a major challenge. Herein, we report a novel approach to prepare palladium nanowire array catalysts by reducting PdCl2 in the pores of anodic aluminum oxide (AAO) templates with backside Al sheets via a hydrothermal process. Suzuki coupling reactions and 4-nitrophenol (4-NP) reduction reactions were employed to study the catalytic activity of the nanocatalysts. The nanocatalysts demonstrated good activity, great thermal stability, easy separation, and excellent reusability in both Suzuki reaction and 4-NP reduction.Keywords: AAO; heterogeneous catalysts; high temperature stability; nanoarray; Pd; Suzuki reaction;
Co-reporter:Shasha Fu, Helin Niu, Zhiyin Tao, Jiming Song, Changjie Mao, Shengyi Zhang, Changle Chen, Dong Wang
Journal of Alloys and Compounds 2013 Volume 576() pp:5-12
Publication Date(Web):5 November 2013
DOI:10.1016/j.jallcom.2013.04.092
•Hollow perovskite-type LaCoO3 is fabricated by green colloidal template method.•Carbonaceous colloids acted as templates and offered internal heat source.•The calcination temperature to form perovskite-type LaCoO3 was dropped to 550 °C.•The photocatalytic properties were studied upon UV irradiation.•Hollow perovskite-type LaCoO3 shows excellent photocatalytic activity on dyes.Hollow perovskite-type LaCoO3 was successfully fabricated by surface-ion adsorption method utilizing the carbonaceous colloids as template under relatively low calcination temperature. Carbonaceous colloids not only acted as templates but also offered internal heat source during calcination process. The impact of calcined temperature and time on the structure and morphology of the product were studied and the possible formation process of perovskite-type LaCoO3 hollow spheres was illustrated. The obtained product was characterized by SEM, TEM, XRD, TG-DSC, ICP-OES, BET and UV–visible absorption spectra. The photocatalytic activities for degradation of methylene blue, methyl orange and neutral red were tested. The good photocatalytic degradation activity of the three different dyes and the band gap of 2.07 eV make it a promising candidate material for photocatalytic applications.
Co-reporter:Dan Zhang, Wenmin Pang, Changle Chen
Journal of Organometallic Chemistry (15 May 2017) Volumes 836–837() pp:
Publication Date(Web):15 May 2017
DOI:10.1016/j.jorganchem.2017.03.007
•Some pyrrolylaldiminato based aluminum complexes were prepared and characterized.•Side arms bearing oxygen, sulfur and SO2 moieties were installed in the ligands.•These complexes are highly active in ring opening polymerization of ε-caprolactone.•The well-controlled behavior was maintained in the absence of initiator.A series of pyrrolylaldiminato ligands and the corresponding five-member-chelate aluminum complexes were prepared and characterized. These metal complexes contain side arms bearing oxygen, sulfur and SO2 moieties, which can influence their catalytic properties. In the presence of one equivalent of benzyl alcohol initiator, these complexes can initiate well-controlled ring opening polymerization of ε-caprolactone with high activities. Most interestingly, the well-controlled behavior was maintained in the absence of the benzyl alcohol initiator.A series of some pyrrolylaldiminato based five-member-chelate aluminum complexes were prepared and applied in the ring opening polymerization of ε-caprolactone.
Co-reporter:Xiang-Kai Kong, Chang-Le Chen and Qian-Wang Chen
Chemical Society Reviews 2014 - vol. 43(Issue 8) pp:NaN2857-2857
Publication Date(Web):2014/02/06
DOI:10.1039/C3CS60401B
Graphene has attracted increasing attention in different scientific fields including catalysis. Via modification with foreign metal-free elements such as nitrogen, its unique electronic and spin structure can be changed and these doped graphene sheets have been successfully employed in some catalytic reactions recently, showing them to be promising catalysts for a wide range of reactions. In this review, we summarize the recent advancements of these new and interesting catalysts, with an emphasis on the universal origin of their catalytic mechanisms. We are full of hope for future developments, such as more precisely controlled doping methods, atom-scale surface characterization technology, generating more active catalysts via doping, and finding wide applications in many different fields.
Co-reporter:Haibo Hu, Changle Chen and Qianwang Chen
Journal of Materials Chemistry A 2013 - vol. 1(Issue 38) pp:NaN6030-6030
Publication Date(Web):2013/05/20
DOI:10.1039/C3TC30657G
Magnetically induced self-assembly is a very powerful method that can quickly, efficiently and reversibly assemble magnetic colloidal particles into ordered structures with tunable photonic properties. The recent developments in the techniques have enabled convenient modulation of photonic properties and easy fabrication of sophisticated photonic structures. As a result, various practical applications such as magnetically controlled display units, photonic humidity sensors, reusable photonic paper/ink, photonic anti-counterfeiting, high resolution full-color photonic printing and invisible photonic printing have been demonstrated. In this feature article, we will describe these recent advances, with special focus on magnetically induced self-assembly of colloidal particles into 1D chainlike photonic structures, and discuss the emerging applications of this new technique.
Co-reporter:Haibo Hu, Hao Zhong, Changle Chen and Qianwang Chen
Journal of Materials Chemistry A 2014 - vol. 2(Issue 19) pp:NaN3702-3702
Publication Date(Web):2014/01/20
DOI:10.1039/C3TC32228A
A high performance photonic anti-counterfeiting watermark that can be incorporated into banknotes has been developed by combining a novel invisible photonic printing with a flexible, translucent and ultra-thin magnetic-responsive photonic display film. The photonic anti-counterfeiting watermark has latent colourful patterns that are lithographically printable and magnetically responsive, and can be easily perceived by the naked eye under magnetic fields. In addition, the distinct differences of the spectral characteristics between the invisible-form and the visible-form of the patterns can be accurately detected by using a special optical instrument, which makes the photonic anti-counterfeiting watermark provide double security information to identify the authenticity of banknotes. Moreover, the strategy allows accurate control of the optical diffraction colour and the structural design of the latent patterns. The fabrication process does not damage the banknotes and allows fast, convenient and scalable production at low-costs. The present work demonstrates that the fabrication of high performance photonic-crystal-based anti-counterfeiting devices on banknotes is possible.
Co-reporter:Liang Zhu, Zhi-Sheng Fu, Hui-Jie Pan, Wei Feng, Changle Chen and Zhi-Qiang Fan
Dalton Transactions 2014 - vol. 43(Issue 7) pp:NaN2906-2906
Publication Date(Web):2013/11/21
DOI:10.1039/C3DT51782A
A series of binuclear nickel/palladium catalysts C4–C7 with conjugated α-diimine ligands were designed, prepared and fully characterized. The binuclear nickel complexes C6 and C7 were activated by modified methylalumoxanes (MMAO) to generate highly active ethylene polymerization catalysts with activities up to 1050 kg [mol (Ni) h]−1. The activity of C7 is twice that of the mononuclear analogue under the same conditions. The effects of the catalyst structure, cocatalyst ratio, polymerization time, solvent and feeding monomer on the catalytic activities, molecular weight and branching structures of the resulting polymers were evaluated. The binuclear palladium complexes C4–C5 produced polyethylene with two separate peaks in GPC curves in ethylene polymerization. In contrast, the mononuclear analogue C3 produces polyethylene with a unimodal GPC curve. Probably, two active species are generated in the binuclear palladium catalyst system and are responsible for the bimodal feature of the GPC curves. The performance of the binuclear palladium complexes in ethylene/methyl acrylate copolymerization was also investigated.
Co-reporter:Xiaohui Hu, Shengyu Dai and Changle Chen
Dalton Transactions 2016 - vol. 45(Issue 4) pp:NaN1503-1503
Publication Date(Web):2015/12/07
DOI:10.1039/C5DT04408A
The synthesis, characterization and ethylene polymerization properties of a series of salicylaldimine Ni(II) complexes with a dibenzhydryl moiety are described. These Ni complexes are designed to bear systematically varied electron donating and withdrawing substituents. These complexes are among the most active salicylaldimine Ni(II) catalysts in ethylene polymerization. Moreover, these complexes demonstrate good thermal stability, maintaining high activity at 80 °C. The polyethylene generated possesses a high molecular weight, moderate branching density and high melting temperature. Surprisingly, the electronic perturbations only exert moderate influence on the ethylene polymerization process despite the covalently close proximity of the electron donating or withdrawing substituents to the metal center. Comparing with the traditional iso-propyl substituted nickel analogue, these new complexes show up to an order of magnitude higher activity, generating polyethylene with much higher molecular weight, similar or slightly lower branching density and much higher melting temperature.
Co-reporter:Wenping Zou, Wenmin Pang and Changle Chen
Inorganic Chemistry Frontiers 2017 - vol. 4(Issue 5) pp:NaN800-800
Publication Date(Web):2017/02/09
DOI:10.1039/C6QI00562D
Two palladium complexes (NHC)Pd(allyl)Cl (NHC = 1,3-Ar2-naphthoquinimidazolylidene, Ar = 2,6-Me2-C6H3, 2,6-iPr2-C6H3) bearing a redox-active naphthoquinone moiety, were prepared and characterized. Electro-chemistry cyclic voltammetry and NMR studies showed that these palladium complexes could be easily reduced and re-oxidized using CoCp2 and [FeCp2][BAF] (BAF = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) reagents. The properties of these neutral and reduced palladium complexes in norbornene, 5-norbornene-2-yl acetate and 1-chloro-1-octyne polymerization were studied. The neutral complexes were active in all of these polymerization reactions in the presence of Na[BAF]. In contrast, the reduced analogues showed very low activity under the same conditions. As such, switchable polymerization could be realized in this catalytic system.
Co-reporter:Xuelin Sui, Changwen Hong, Wenmin Pang and Changle Chen
Inorganic Chemistry Frontiers 2017 - vol. 1(Issue 5) pp:NaN972-972
Publication Date(Web):2016/12/14
DOI:10.1039/C6QM00235H
Previously, it was demonstrated that nickel complexes bearing unsymmetrical α-diimine ligands generated polymers with a broad molecular weight distribution in ethylene polymerization. In this contribution, the influence of some unsymmetrical α-diimine ligands on the catalytic properties of their palladium complexes was investigated in ethylene polymerization, ethylene–methyl acrylate copolymerization and 1-hexene polymerization. Quite interestingly, the unsymmetrical α-diimine ligand structures did not lead to a broad molecular weight distribution in these polymerization and copolymerization reactions. In addition, the influence of different substituents (OMe, Me, Cl and NO2) and different backbone structures was studied. The palladium complexes bearing electron-donating groups showed higher thermal stability and afforded polymers with a much higher molecular weight. The palladium complex bearing naphthalene backbone showed a much lower catalytic activity, generating polymers or copolymers with a much lower molecular weight. The mechanical and surface properties of the resulting polymer and copolymer were also investigated.
![Benzenesulfonic acid, 2-[(2',6'-dimethoxy[1,1'-biphenyl]-2-yl)phenylphosphino]-](/data/chemimg/163700/1312097-12-3.png)
![Benzenesulfonic acid, 2-[(2',6'-dimethoxy[1,1'-biphenyl]-2-yl)phenylphosphino]-](/data/chemimg/163700/1312097-12-3_b.png)
![2-Butanone, 3-[[2,6-bis(1-methylethyl)phenyl]imino]-](http://img.cochemist.com/ccimg/490100/490022-24-7.png)
![2-Butanone, 3-[[2,6-bis(1-methylethyl)phenyl]imino]-](http://img.cochemist.com/ccimg/490100/490022-24-7_b.png)
![Phenol, 2-[[[2,6-bis(1-methylethyl)phenyl]imino]methyl]-4,6-bis(1,1-dimethylethyl)-](/data/chemimg/135600/210882-24-9.png)
![Phenol, 2-[[[2,6-bis(1-methylethyl)phenyl]imino]methyl]-4,6-bis(1,1-dimethylethyl)-](/data/chemimg/135600/210882-24-9_b.png)
![1(2H)-Acenaphthylenone, 2-[[2,6-bis(1-methylethyl)phenyl]imino]-](http://img.cochemist.com/ccimg/187700/187605-59-0.png)
![1(2H)-Acenaphthylenone, 2-[[2,6-bis(1-methylethyl)phenyl]imino]-](http://img.cochemist.com/ccimg/187700/187605-59-0_b.png)
