Polymerization Of Norbornene Research Articles

In Situ Generated Ruthenium-Arene Catalyst for Photoactivated Ring-Opening Metathesis Polymerization through Photolatent N-Heterocyclic Carbene Ligand.

1,3-Bis(mesityl)imidazolium tetraphenylborate (IMesH+ BPh4- ) can be synthesized in one step by anion metathesis between the corresponding imidazolium chloride and sodium tetraphenylborate. In the presence of 2-isopropylthioxanthone (sensitizer), an IMes N-heterocyclic carbene (NHC) ligand can be photogenerated under irradiation at 365 nm through coupled electron/proton transfer reactions. By combining this tandem NHC photogenerator system with metathesis inactive [RuCl2 (p-cymene)]2 precatalyst, the highly active RuCl2 (p-cymene)(IMes) complex can be formed in situ, enabling a complete ring-opening metathesis polymerization (ROMP) of norbornene in the matter of minutes at room temperature. To the best of our knowledge, this is the first example of a photogenerated NHC. Its exploitation in photoROMP has resulted in a simplified process compared to current photocatalysts, because only stable commercial or easily synthesized reagents are required.

Cis-Specific Chain Transfer Ring-Opening Metathesis Polymerization Using a Vanadium(V) Alkylidene Catalyst for Efficient Synthesis of End-Functionalized Polymers

Highly efficient synthesis of end-functionalized polymers has been achieved by combined cis-specific ring-opening metathesis polymerization (ROMP) of norbornene with terminal olefins (1-hexene, allyltrimethylsilane (ATMS), etc.) as the chain transfer (cross metathesis) agent at 80 °C in the presence of V(CHSiMe3)(N-2,6-Cl2C6H3)[OC(CF3)3](PMe3)2. The ROMP proceeds with high activity and high cis selectivity (97–98%) upon addition of PMe3, and the Mn values could be controlled by varying the concentration of terminal olefins; the activity at 80 °C was not affected by the ATMS concentrations (5.0–50.0 mol %, TOF 1860–1890 min–1 ((1.12–1.13) × 105 h–1)).

Phosphine (oxide)‐(thio) phenolate palladium complexes: Synthesis, characterization and (co)polymerization of norbornene

A series of palladium complexes (2a–2g) (2a: [6‐tBu‐2‐PPh2‐C6H3O]PdMe(Py); 2b: [6‐C6F5–2‐PPh2‐C6H3O]PdMe(Py); 2c: [6‐tBu‐2‐PPhtBu‐C6H3O]PdMe(Py); 2d: [2‐PPhtBu‐C6H4O] PdMe(Py); 2e: [6‐SiMe3–2‐PPh2‐C6H3O]PdMe(Py); 2f: [2‐tBu‐6‐(Ph2P=O)‐C6H3O]PdMe(Py); 2g: [6‐SiMe3–2‐(Ph2P=O)‐C6H3S]PdMe(Py)) bearing phosphine (oxide)‐(thio) phenolate ligand have been efficiently synthesized and characterized. The solid‐state structures of complexes 2d, 2f and 2g have been further confirmed by single‐crystal X‐ray diffraction, which revealed a square‐planar geometry of palladium center. In the presence of B(C6F5)3, these complexes can be used as catalysts to polymerize norbornene (NB) with relatively high yields, producing vinyl‐addition polymers. Interestingly, 2a/B(C6F5)3 system catalyzed the polymerization of NB in living polymerization manner at high temperature (polydispersity index 1.07, Mn up to 1.5 × 104). The co‐polymerization of NB and polar monomers was also studied using catalysts 2a and 2f. All the obtained co‐polymers could dissolve in common solvent.

Single Turnover at Molecular Polymerization Catalysts Reveals Spatiotemporally Resolved Reactions.

Multiple active individual molecular ruthenium catalysts have been pinpointed within growing polynorbornene, thereby revealing information on the reaction dynamics and location that is unavailable through traditional ensemble experiments. This is the first single-turnover imaging of a molecular catalyst by fluorescence microscopy and allows detection of individual monomer reactions at an industrially important molecular ruthenium ring-opening metathesis polymerization (ROMP) catalyst under synthetically relevant conditions (e.g. unmodified industrial catalyst, ambient pressure, condensed phase, ca. 0.03 m monomer). These results further establish the key fundamentals of this imaging technique for characterizing the reactivity and location of active molecular catalysts even when they are the minor components.

Synthesis of Polyisobutylene Bottlebrush Polymers via Ring-Opening Metathesis Polymerization

Polyisobutylene (PIB)-based bottlebrush polymers were synthesized via ring-opening metathesis polymerization (ROMP) of norbornene- and oxanorbornene-terminated PIB macromonomers (MM) initiated by Grubbs third-generation catalyst ((H2IMes2)(pyr)2(Cl)2Ru═CHPh) (G3). While both MMs reached greater than 97% conversion as measured by 1H NMR, the rate of propagation of PIB norbornene was measured to be 2.9 times greater than that of PIB oxanorbornene MMs of similar molecular weight (MW). The slower rate of propagation of the oxanorbornene MM was attributed to interaction between the electron-rich oxygen bridge and the metal center of G3, which slowed but did not inhibit polymerization. Both types of MMs demonstrated controlled/“living” polymerization behavior, and brush polymers with MWs up to ∼700 kg/mol with narrow dispersity (Đ ≤ 1.04) were achieved.

Graft polymerization of norbornene onto polyurethane and the characterization of its effect on the shape recovery and low-temperature flexibility of polyurethane

Graft polymerization of norbornene monomers onto polyurethane (PU) was tested to reduce the intermolecular attractions between PUs using the rigid bicyclic ring structure of norbornene, to control the soft segment thermal properties, and to enhance the tensile, shape memory, and low-temperature flexibility properties compared with those of unmodified PU. The soft segment crystallization temperature (T c) sharply decreased with the increase in norbornene, whereas the soft segment melting temperature (T m) was not significantly changed by the norbornene content. However, the glass transition temperature (T g) increased with the incorporation of norbornene. The tensile strength sharply increased with the increase in norbornene due to the chemical cross-linking between the grafted poly(norbornene), whereas a significant decrease in the maximum strain was not observed. The shape recovery at 10 °C sharply increased from 47% to approximately 90% after the graft polymerization of norbornene, and the shape retention at −25 °C decreased with the increase in norbornene. Finally, the graft polymerization of norbornene onto PU demonstrated enhanced low-temperature flexibility due to the reduced restrictions of rotational and translational mobility.

Bidirectional metal‐free ROMP from difunctional organic initiators

Bidirectional metal‐free ROMP from difunctional organic initiators

α‐Diimine–Palladium Complexes Incorporated in Vinylic‐Addition Polynorbornenes: Synthesis and Catalytic Activity

α‐Diimine polymeric ligands have been synthesized using the bicyclic norbornane structure, present in vinylic‐addition polynorbornene (VA‐PNB). The VA‐PNB–diimine ligands have been prepared by functionalization of the copolymer obtained by Ni‐catalyzed polymerization of norbornene and norbornenylcarbonate. Immobilized palladium complexes of the type VA‐PNB–diimine–PdX2 have been prepared, and their catalytic activity has been tested. The trifluoroacetato complex (X = CF3COO) can be used as a recyclable precatalyst in the Suzuki reaction. It is the source of minute amounts of homogeneous palladium active species, which carry out the catalysis with high turnover numbers. The recovered polymeric complex can be reused several times with no significant loss of activity. The polymeric analogue to Brookhart's catalyst, VA‐PNB–diimine–PdMeCl, can also polymerize ethylene, although it is less active than its monomeric counterparts.

Highly active nickel(II) and palladium(II) complexes bearing N,N,P tridentate ligand for vinyl addition polymerization of norbornene

A series of nickel (II) complexes (1a-4a) and palladium (II) complexes (1b-4b) bearing N,N,P tridentate ligands derived from amino-alkyl phosphines and 2-pyridinecarboxaldehyde and 2-quinolinecarboxaldehyde were synthesized and characterized. X-ray diffraction analysis revealed that complexes 1a, 4a, and 2b adopted square-pyramidal geometry, trigonal bipyramid, and distorted square-planar geometry, respectively. Activated by methylaluminoxane (MAO), all the complexes were highly active for norbornene polymerization in a vinyl addition fashion, affording high molecular weight polymers with narrow molecular weight distributions. The activities of palladium complexes are particularly notable; the highest activity reached 2.45×108g PNB (mol of Ni)−1h−1. The activities of the complexes were affected by the ligand structure as well as the reaction parameters such as polymerization temperature, time, and cocatalyst loading.

ABC Supramolecular Triblock Copolymer by ROMP and ATRP

We report the controlled polymerization of three heterotelechelic polymers from supramolecular motif-bearing initiators, their assembly into supramolecular A/B/C triblock copolymers, the morphology of the resulting block copolymers, and their disassembly. The individual blocks are synthesized in a controlled or living fashion via ring-opening metathesis polymerization (ROMP) of norbornenes (block B) or atom-transfer radical polymerization (ATRP) of styrenes (block A) and methacrylates (block C). The building blocks are assembled via metal-coordination between blocks A and B using a palladated SCS pincer complex and pyridine, and hydrogen bonding between blocks B and C using Hamilton Wedge and barbituric acid derivatives. Scanning-transmission electron microscopy and small-angle X-ray scattering reveal lamellar domains of approximately 23, 15, and 21 nm for bulk samples of the A/B and B/C diblock copolymers and A/B/C triblock copolymers, with 1:1 and 1:1:1 block feed ratios, respectively. Nanoscale feature...

Ring opening metathesis polymerization of norbornene and tetracyclododecene with cyclooctene by using (arylimido)vanadium(V)–alkylidene catalyst

ABSTRACTRing opening metathesis polymerizations (ROMP) of norbornene (NBE), tetracyclododecene (TCD) in the presence of cis‐cyclooctene (COE) using vanadium‐alkylidene catalyst, V(CHSiMe3)(N‐2,6‐Cl2C6H3)(OC6F5)(PMe3)2 (1), were explored. The polymerizations with TCD afforded high‐molecular‐weight polymers (Mn = 19,500–47,400) with low PDI (Mw/Mn) values (1.18–1.38) which possess microstructure of repeated ring‐opened TCD and certain methylene units by incorporation of ring‐opened COE on the basis of microstructure analysis by NMR spectra and DSC thermograms; hydrogenated copolymer possessed melting temperature at 294 °C. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3067–3074

Redox Control in Olefin Polymerization Catalysis by Phosphine–Sulfonate Palladium and Nickel Complexes

Two phosphine–sulfonate ligands, bearing both the ferrocene and the bi‐aryl units, were prepared and characterized. The corresponding palladium and nickel complexes are active in ethylene polymerization. In both the palladium and the nickel systems, the oxidation of the ferrocene unit leads to a decrease in catalytic activities and the polymer molecular masses. Interestingly, the neutral palladium catalyst is not active for norbornene polymerization, while the oxidized analogue shows good activity. As such, switchable polymerization could be achieved.

Synthesis, characterization, and olefin polymerization of half-sandwich Ir, Rh, Ru metallacycle enclosing a nickel in the center

Reactions of binuclear [Cp*Ir(μ-Cl)Cl]2 (Cp* = pentamethylcyclopentadienyl), [Cp*Rh(μ-Cl)Cl]2 and [(p-cymene)Ru(μ-Cl)Cl]2 with 2 equiv. AgOTf (OTf = O3SCF3) followed by addition of one equiv. (m-pyridyl)N=C(C10H6)C=N(m-pyridyl) (mPy-bian) linker and NiCl2·DME (DME = 1,2-dimethoxyethane) in methanol gave heterometallic cationic metallacycles [Cp*4Ir4(μ-Cl)4(μ-mPy-bian)2NiCl2](OTf)4 (1a), [Cp*4Rh4(μ-Cl)4(μ-mPy-bian)2NiCl2](OTf)4 (1b), and [(p-cymene)4Ru4(μ-Cl)4(μ-mPybian)2NiCl2](OTf)4 (1c), respectively. All the complexes are characterized by IR, NMR spectroscopy, and elemental analysis. Ni K-edge X-ray absorption spectroscopy (XAS) studies on 1a–1c reveal that nickel is six-coordinate with four nitrogens and two chlorides. Upon activation with MAO, 1a–1c showed moderate to good catalytic activity for ethylene and norbornene polymerization.

Copolymerization of Norbornene and Norbornadiene Using a cis-Selective Bimetallic W-Based Catalytic System.

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.

Coil‐helix and sheet‐helix block copolymers via macroinitiation from telechelic ROMP polymers

ABSTRACTCoil‐helix and sheet‐helix block copolymers are synthesized by combining the ring‐opening metathesis polymerization (ROMP) of norbornene or paracyclophanediene with the anionic polymerization of phenyl isocyanide. Key to the design is the use of an μ‐ethynyl palladium (II) functionalized chain‐transfer agent (CTA) that can be exploited in a stepwise manner for the termination of ROMP and the initiation of the anionic polymerization. Both the coil‐ and sheet‐macroinitiators, and the ensuing covalent block copolymers, are analyzed using 1H NMR spectroscopy and gel‐permeation chromatography. In all cases, the Pd‐end group is maintained and all polymers demonstrate a monomodal distribution with dispersities (Đ) of 1.1–1.4. The resulting helix‐coil and helix‐sheet block copolymers formed by the macroinitiation route still demonstrate their intrinsic properties (fluorescence, preferential helix‐sense). © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2991–2998

Mononuclear Nickel(II) Complexes with Schiff Base Ligands: Synthesis, Characterization, and Catalytic Activity in Norbornene Polymerization.

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.

A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes.

Norbornene can be polymerized by a variety of mechanisms, including insertion polymerization whereby the double bond is polymerized and the bicyclic nature of the monomer is conserved. The resulting polymer, polynorbornene, has a very high glass transition temperature, Tg, and interesting optical and electrical properties. However, the polymerization of functional norbornenes by this mechanism is complicated by the fact that the endo substituted norbornene monomer has, in general, a very low reactivity. Furthermore, the separation of the endo substituted monomer from the exo monomer is a tedious task. Here, we present a simple protocol for the polymerization of substituted norbornenes (endo:exo ca. 80:20) bearing either a carboxylic acid or a pendant double bond. The process does not require that both isomers be separated, and proceeds with low catalyst loadings (0.01 to 0.02 mol%). The polymer bearing pendant double bonds can be further transformed in high yield, to afford a polymer bearing pendant epoxy groups. These simple procedures can be applied to prepare polynorbornenes with a variety of functional groups, such as esters, alcohols, imides, double bonds, carboxylic acids, bromo-alkyls, aldehydes and anhydrides.

A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes

A Simple and Efficient Protocol for the Catalytic Insertion Polymerization of Functional Norbornenes

Investigation of Tacticity and Living Characteristics of Photoredox-Mediated Metal-Free Ring-Opening Metathesis Polymerization.

This study investigated the microstructures of polymers produced via photoredox-mediated metal-free ring-opening metathesis polymerization. Polynorbornene, poly(exo-dihydrodicyclopentadiene), and poly(endo-dicyclopentadiene) were found to have cis olefin contents of 23%, 24%, and 28%, respectively. Additionally, the cis/trans ratio remained consistent during the course of norbornene polymerization. Polymer tacticity was evaluated by quantitative 13 C NMR spectroscopy, which revealed each polymer to be largely atactic. Specifically, the three polymers were estimated to be 33%, 58%, and 55% syndiotactic, respectively. In parallel, this study also explored the ability to produce diblock copolymers from norbornene and exo-dihydrodicyclopentadiene. Successful diblock copolymerization was achieved using either monomer order. In each case, however, the results suggested to us that chain-chain coupling (increased molecular weight) and irreversible termination (dead chains observed during attempted chain extension) occurred when reaction times were extended.

Efficient NIR (near-infrared) luminescent ZnLn-grafted (Ln=Nd, Yb or Er) PNBE (Poly(norbornene))

Through the ring-opening metathesis polymerization (ROMP) of norbornene (NBE) with each of allyl-containing complex monomers [Zn(L)2(µ1-OAc)Ln(µ2-OAc)2] (Ln=La, 1; Nd, 2; Yb, 3; Er, 4 or Gd, 5; HL=4-allyl-2-(1H-benzo[d]imidazol-2-yl)-6-methoxyphenol), a series of ZnLn-grafted polymers Poly([Zn(L)2(µ1-OAc)Ln(µ2-OAc)2]-co-NBE) with desired physical properties were obtained, respectively. Within near-infrared (NIR) luminescent polymers, Poly(3-co-NBE) endows an attractive quantum yield of 1.47% in solid state, and exhibits an effective prevention of high-concentration self-quenching.