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Polymers
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Metal Complexes-Mediated Catalysis in Polymerization
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Metal Complexes-Mediated Catalysis in Polymerization

A special issue of Polymers (ISSN 2073-4360).

Deadline for manuscript submissions: closed (28 February 2017) | Viewed by 64287

Special Issue Editor

Prof. Dr. Marinos Pitsikalis

E-Mail Website
Guest Editor
Laboratory of Industrial Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, 15771 Zografou, Greece
Interests: polymer synthesis; polymer characterization; self-assembly of copolymers in selective solvents
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

One of the ultimate challenges in polymer chemistry is the development of new synthetic methods for the polymerization of a wide range of monomers leading to products with well-defined molecular characteristics (molecular weight and molecular weight distribution), stereochemistry and architecture. In this respect, catalytic polymerization is now considered as one of the most important research frontiers in polymer chemistry and technology. It has become the backbone of several significant branches of the plastics and rubber industries occupying the most prominent place in the market.
Transition metal chemistry has witnessed a spectacular growth in the past two decades. The design and application of transition metal complexes as catalysts has been recognized as the most powerful tool for the polymerization of non-polar and polar monomers. Research has been mainly focused on the polymerization of the commercially most important monomers, such as ethylene, propylene and α-olefins. However, other monomers, such as (meth)acrylates, lactones, lactides and isocyanates, have been polymerized by catalytic polymerization techniques.
This Special Issue is focused on the recent developments in the synthesis of linear and non-linear homo- and copolymers by metal complexes-mediated catalytic polymerization. Polymerization of new monomers, design and synthesis of novel catalytic species able to promote polymerization reactions, kinetics of polymerization, mechanistic studies, synthesis of complex macromolecular architectures in combination with other polymerization techniques, molecular and structural characterization of the polymeric products, preparation of polymer nanocomposites with inorganic materials (silica, alumina, clays etc.), carbon nanotubes or graphene are among the topics that will be covered. The catalytic species include Ziegler-Natta catalysts, metallocene and half-metallocene complexes of the 3rd, 4th, and 5th groups of the periodic table, non-metallocene complexes bearing diamido, alkylthio, amine-phenolate, etc., ligands, late transition metal complexes based on nickel, palladium, copper and ruthenium, molybdenum, etc., complexes for Ring Opening Metathesis Polymerization reactions of cycloolefins and alkynes. Both original contributions and reviews are welcome.

Professor Marinos Pitsikalis
Guest Editor

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Keywords

  • Catalytic polymerization
  • Ziegler-Natta catalysts
  • Metallocene catalysts
  • Half-metallocene catalysts
  • Non-metallocene catalysts
  • Late transition metal catalysts
  • Ring Opening Metathesis Polymerization catalysts
  • Linear and non-linear homo- and copolymers
  • Polymer nanocomposites
  • Polymerization kinetics
  • Polymerization mechanism
  • Molecular and structural characterization

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Published Papers (9 papers)

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Research

2140 KiB  
Article
Synthesis, Characterization and Thermal Properties of Poly(ethylene oxide), PEO, Polymacromonomers via Anionic and Ring Opening Metathesis Polymerization
by George V. Theodosopoulos, Christos Zisis, Georgios Charalambidis, Vasilis Nikolaou, Athanassios G. Coutsolelos and Marinos Pitsikalis
Polymers 2017, 9(4), 145; https://doi.org/10.3390/polym9040145 - 21 Apr 2017
Cited by 32 | Viewed by 7889
Abstract
Branched polymers are a valuable class of polymeric materials. In the present study, anionic polymerization techniques were employed for the synthesis of low molecular weight poly(ethylene oxide) (PEO) macromonomers bearing norbornenyl end groups. The macromonomers were characterized by SEC, MALDI-TOF and NMR spectroscopy. [...] Read more.
Branched polymers are a valuable class of polymeric materials. In the present study, anionic polymerization techniques were employed for the synthesis of low molecular weight poly(ethylene oxide) (PEO) macromonomers bearing norbornenyl end groups. The macromonomers were characterized by SEC, MALDI-TOF and NMR spectroscopy. Subsequent ring opening metathesis polymerization (ROMP) of the macromonomers using ruthenium catalysts (Grubbs catalysts of the 1st, 2nd and 3rd generations) afforded the corresponding polymacromonomers. The effects of the macromonomer molecular weight, the type of the catalyst, the nature of the solvent, the monomer concentration and the polymerization temperature on the molecular characteristics of the branched polymers were examined in detail. The crystallization behavior of the macromonomers and the corresponding polymacromonomers were studied by Differential Scanning Calorimetry (DSC). The thermal stability and the kinetics of the thermal decomposition of the samples were also studied by Thermogravimetric Analysis (TGA). The activation energies of the thermal decomposition were analyzed using the Ozawa–Flynn–Wall and Kissinger methodologies. Full article
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
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3351 KiB  
Article
Copolymerization of Norbornene and Norbornadiene Using a cis-Selective Bimetallic W-Based Catalytic System
by Grigorios Raptopoulos, Katerina Kyriakou, Gregor Mali, Alice Scarpellini, George C. Anyfantis, Thomas Mavromoustakos, Marinos Pitsikalis and Patrina Paraskevopoulou
Polymers 2017, 9(4), 141; https://doi.org/10.3390/polym9040141 - 18 Apr 2017
Cited by 12 | Viewed by 6609
Abstract
The bimetallic cluster Na[W2(μ-Cl)3Cl4(THF)2]·(THF)3 ({W2}, {W 3 W}6+, a′2e′4), which features a triple metal-metal bond, is a highly efficient room-temperature initiator for ring opening [...] Read more.
The bimetallic cluster Na[W2(μ-Cl)3Cl4(THF)2]·(THF)3 ({W2}, {W 3 W}6+, a′2e′4), which features a triple metal-metal bond, is a highly efficient room-temperature initiator for ring opening metathesis polymerization (ROMP) of norbornene (NBE) and norbornadiene (NBD), providing high-cis polymers. In this work, {W2} was used for the copolymerization of the aforementioned monomers, yielding statistical poly(norbornene)/poly(norbornadiene) PNBE/PNBD copolymers of high molecular weight and high-cis content. The composition of the polymer chain was estimated by 13C CPMAS NMR data and it was found that the ratio of PNBE/PNBD segments in the polymer chain was relative to the monomer molar ratio in the reaction mixture. The thermal properties of all copolymers were similar, resembled the properties of PNBD homopolymer and indicated a high degree of cross-linking. The morphology of all materials in this study was smooth and non-porous; copolymers with higher PNBE content featured a corrugated morphology. Glass transition temperatures were lower for the copolymers than for the homopolymers, providing a strong indication that those materials featured a branched-shaped structure. This conclusion was further supported by viscosity measurements of copolymers solutions in THF. The molecular structure of those materials can be controlled, potentially leading to well-defined star polymers via the “core-first” synthesis method. Therefore, {W2} is not only a cost-efficient, practical, highly active, and cis-stereoselective ROMP-initiator, but it can also be used for the synthesis of more complex macromolecular structures. Full article
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
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2669 KiB  
Article
Stereoregular Brush Polymers and Graft Copolymers by Chiral Zirconocene-Mediated Coordination Polymerization of P3HT Macromers
by Yang Wang, Travis S. Bailey, Miao Hong and Eugene Y.-X. Chen
Polymers 2017, 9(4), 139; https://doi.org/10.3390/polym9040139 - 13 Apr 2017
Cited by 8 | Viewed by 7977
Abstract
Two poly(3-hexylthiophene) (P3HT) macromers containing a donor polymer with a polymerizable methacrylate (MA) end group, P3HT-CH2-MA and P3HT-(CH2)2-MA, have been synthesized, and P3HT-(CH2)2-MA has been successfully homopolymerized and copolymerized with methyl methacrylate (MMA) [...] Read more.
Two poly(3-hexylthiophene) (P3HT) macromers containing a donor polymer with a polymerizable methacrylate (MA) end group, P3HT-CH2-MA and P3HT-(CH2)2-MA, have been synthesized, and P3HT-(CH2)2-MA has been successfully homopolymerized and copolymerized with methyl methacrylate (MMA) into stereoregular brush polymers and graft copolymers, respectively, using chiral ansa-zirconocene catalysts. Macromer P3HT-CH2-MA is too sterically hindered to polymerize by the current Zr catalysts, but macromer P3HT-(CH2)2-MA is readily polymerizable via either homopolymerization or copolymerization with MMA in a stereospecific fashion with both C2-ligated zirconocenium catalyst 1 and Cs-ligated zirconocenium catalyst 2. Thus, highly isotactic (with mm% ≥ 92%) and syndiotactic (with rr% ≥ 93%) brush polymers, it-PMA-g-P3HT and st-PMA-g-P3HT, as well as well-defined stereoregular graft copolymers with different grafted P3HT densities, it-P(M)MA-g-P3HT and st-P(M)MA-g-P3HT, have been synthesized using this controlled coordination-addition polymerization system under ambient conditions. These stereoregular brush polymers and graft copolymers exhibit both thermal (glass and melting) transitions with Tg and Tm values corresponding to transitions within the stereoregular P(M)MA and crystalline P3HT domains. Acceptor molecules such as C60 can be effectively encapsulated inside the helical cavity of st-P(M)MA-g-P3HT to form a unique supramolecular helical crystalline complex, thus offering a novel strategy to control the donor/acceptor solar cell domain morphology. Full article
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
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663 KiB  
Article
Living Polymerization of Propylene with ansa-Dimethylsilylene(fluorenyl)(cumylamido) Titanium Complexes
by Huajin Wang, Xinwei Wang, Yanjie Sun, Hailong Cheng, Takeshi Shiono and Zhengguo Cai
Polymers 2017, 9(4), 131; https://doi.org/10.3390/polym9040131 - 5 Apr 2017
Cited by 3 | Viewed by 4697
Abstract
A series of ansa-silylene(fluorenyl)(amido) titanium complexes (1a–1c, 2a, and 2b) bearing various substituents on the amido and fluorenyl ligands are synthesized and characterized by elemental analysis, 1H NMR, and single crystal X-ray analysis. The coordination [...] Read more.
A series of ansa-silylene(fluorenyl)(amido) titanium complexes (1a–1c, 2a, and 2b) bearing various substituents on the amido and fluorenyl ligands are synthesized and characterized by elemental analysis, 1H NMR, and single crystal X-ray analysis. The coordination mode of the fluorenyl ligand to the titanium metal is η3 manner in each complex. The propylene polymerization is conducted with these complexes at 0 and 25 °C in a semi batch-type method, respectively. The catalytic activity of 1a–1c bearing cumyl-amido ligand is much higher than that of 2a and 2b bearing naphthyl group in amido ligand. High molecular weight polypropylenes are obtained with narrow molecular weight distribution, suggesting a living nature of these catalytic systems at 0 °C. The polymers produced are statistically atactic, regardless of the structure of the complex and the polymerization temperature. Full article
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
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756 KiB  
Article
Direct Synthesis of Branched Carboxylic Acid Functionalized Poly(1-octene) by α-Diimine Palladium Catalysts
by Lihua Guo, Chen Zou, Shengyu Dai and Changle Chen
Polymers 2017, 9(4), 122; https://doi.org/10.3390/polym9040122 - 27 Mar 2017
Cited by 35 | Viewed by 7971
Abstract
In this work, we studied propylene polymerization using some α-diimine palladium catalysts with systematically varied ligand sterics. In propylene polymerization, the ligand steric effect exhibits significant variations on the catalytic activity, polymer molecular weight, and branching density. However, the regio control for the [...] Read more.
In this work, we studied propylene polymerization using some α-diimine palladium catalysts with systematically varied ligand sterics. In propylene polymerization, the ligand steric effect exhibits significant variations on the catalytic activity, polymer molecular weight, and branching density. However, the regio control for the polymer microstructure is poor. Furthermore, copolymerization of 1-octene with the highly challenging and biorenewable comonomer acrylic acid was investigated. High copolymer molecular weights and high comonomer incorporation ratios could be achieved in this system. This study provides a novel access for the direct synthesis of branched carboxylic acid functionalized polyolefins. Full article
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
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4599 KiB  
Article
Chiral MnIII (Salen) Covalently Bonded on Modified ZPS-PVPA and ZPS-IPPA as Efficient Catalysts for Enantioselective Epoxidation of Unfunctionalized Olefins
by Xiaochuan Zou, Cun Wang, Yue Wang, Kaiyun Shi, Zhongming Wang, Dongwei Li and Xiangkai Fu
Polymers 2017, 9(3), 108; https://doi.org/10.3390/polym9030108 - 17 Mar 2017
Cited by 11 | Viewed by 6260
Abstract
Chiral MnIII (salen) complex supported on modified ZPS-PVPA (zirconium poly(styrene-phenylvinylphosphonate)) and ZPS-IPPA (zirconium poly(styrene-isopropenyl phosphonate)) were prepared using –CH2Cl as a reactive surface modifier by a covalent grafting method. The supported catalysts showed higher chiral induction (ee: 72%–83%) compared [...] Read more.
Chiral MnIII (salen) complex supported on modified ZPS-PVPA (zirconium poly(styrene-phenylvinylphosphonate)) and ZPS-IPPA (zirconium poly(styrene-isopropenyl phosphonate)) were prepared using –CH2Cl as a reactive surface modifier by a covalent grafting method. The supported catalysts showed higher chiral induction (ee: 72%–83%) compared with the corresponding homogeneous catalyst (ee: 54%) for asymmetric epoxidation of α-methylstrene in the presence of 4-phenylpyridine N-oxide (PPNO) as axial base using NaClO as an oxidant. ZPS-PVPA-based catalyst 1, with a larger pore diameter and surface area, was found to be more active than ZPS-IPPA-based catalyst 2. In addition, bulkier alkene-like indene, was efficiently epoxidized with these supported catalysts (ee: 96%–99%), the results were much higher than those for the homogeneous system (ee: 65%). Moreover, the prepared catalysts were relatively stable and can be recycled at least eight times without significant loss of activity and enantioselectivity. Full article
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
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1945 KiB  
Article
Mononuclear Nickel(II) Complexes with Schiff Base Ligands: Synthesis, Characterization, and Catalytic Activity in Norbornene Polymerization
by Yi-Mei Xu, Kuan Li, Yuhong Wang, Wei Deng and Zi-Jian Yao
Polymers 2017, 9(3), 105; https://doi.org/10.3390/polym9030105 - 16 Mar 2017
Cited by 17 | Viewed by 7157
Abstract
The nickel(II) catalyst has manifested higher catalytic activity compared to that of other late transition metal catalysts for norbornene polymerization. Therefore, several structurally similar trans-nickel(II) compounds of N,O-chelate bidentate ligands were synthesized and characterized. Both the electronic effect and [...] Read more.
The nickel(II) catalyst has manifested higher catalytic activity compared to that of other late transition metal catalysts for norbornene polymerization. Therefore, several structurally similar trans-nickel(II) compounds of N,O-chelate bidentate ligands were synthesized and characterized. Both the electronic effect and the steric hindrance influence polymerization. The molecular structures of 2, 4 and 5 were further confirmed by single-crystal X-ray diffraction. Full article
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
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3899 KiB  
Article
Microwave Assisted Reduction of Pt-Catalyst by N-Phenyl-p-Phenylenediamine for Proton Exchange Membrane Fuel Cells
by Ming-Jer Tsai, Tar-Hwa Hsieh, Yen-Zen Wang, Ko-Shan Ho and Chia-Yun Chang
Polymers 2017, 9(3), 104; https://doi.org/10.3390/polym9030104 - 15 Mar 2017
Cited by 9 | Viewed by 6313
Abstract
The presence of N-phenyl-p-phenylenediamine (PPDA: a dimer of aniline) during microwave (MW) irradiation can significantly improve Pt-loading on the XC72 carbon matrix as a catalyst support of proton exchange membrane fuel cells (PEMFCs). PPDA is converted to an emeraldine base [...] Read more.
The presence of N-phenyl-p-phenylenediamine (PPDA: a dimer of aniline) during microwave (MW) irradiation can significantly improve Pt-loading on the XC72 carbon matrix as a catalyst support of proton exchange membrane fuel cells (PEMFCs). PPDA is converted to an emeraldine base state during MW-assisted redox reaction, which is characterized by both FTIR and Raman spectra. The increased degree of conjugation from the formation of quinone-state of PPDA is confirmed by UV-VIS spectra. TEM micrographs and residue weights obtained from the TGA thermograms illustrate the particle size and Pt-loading percent of Pt nanoparticles (NPs) after MW irradiation, respectively. X-ray diffraction patterns indicate Pt NPs are successfully loaded on XC72 by MW irradiation corresponding to hydrothermal method. The single cell performance demonstrates an increasing power and maximum current density when Pt-catalyst of membrane exchanged assembly (MEA) is prepared by MW-assisted reduction in the presence of PPDA. Full article
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
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3053 KiB  
Article
DFT Studies on cis-1,4-Polymerization of Dienes Catalyzed by a Cationic Rare-Earth Metal Complex Bearing an Ancillary PNP Ligand
by Xingbao Wang, Xiaohui Kang, Guangli Zhou, Jingping Qu, Zhaomin Hou and Yi Luo
Polymers 2017, 9(2), 53; https://doi.org/10.3390/polym9020053 - 7 Feb 2017
Cited by 15 | Viewed by 8086
Abstract
Dnsity functional theory (DFT) calculations have been carried out for the highly selective cis-1,4-polymerization of butadiene catalyzed by a cationic rare-earth metal complex bearing an ancillary PNP ligand. It has been found that the chain initiation and propagation of butadiene polymerization occurs [...] Read more.
Dnsity functional theory (DFT) calculations have been carried out for the highly selective cis-1,4-polymerization of butadiene catalyzed by a cationic rare-earth metal complex bearing an ancillary PNP ligand. It has been found that the chain initiation and propagation of butadiene polymerization occurs via the favorable cis-1,4-insertion route. The trans-1,4 and 1,2-insertion are unfavorable both kinetically and thermodynamically. The chain growth follows the π-allyl-insertion mechanism. The analyses of energy decomposition of transition states indicate that the likelihood of rival insertion pathways is predominantly controlled by the interaction energy of butadiene with a metal center and the deformation energy of butadiene moiety. The electronic factor of the central metal has a decisive influence on the cis- vs. trans-insertion and the regioselectivity (cis-1,4- vs. cis-1,2-insertion) is mainly determined by steric hindrance. Tetrahydrofuran (THF) coordination made monomer insertion less favorable compared with THF-free case and had more noticeable impact on the trans-monomer insertion compared with the cis case. During the chain propagation, cis-insertion of monomer facilitates THF de-coordination and the THF molecule could therefore dissociate from the central metal. Full article
(This article belongs to the Special Issue Metal Complexes-Mediated Catalysis in Polymerization)
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