Ethylene‐Norbornene Terpolymerization with 5‐Vinyl‐2‐norbornene Using Single‐Site Catalysts

The incorporation of 5‐vinyl‐2‐norbornene (VNB) into ethylene‐norbornene copolymer was investigated with catalysts [Ph₂C(Fluo)(Cp)]ZrCl₂ ( 1 ), rac‐[Et(Ind)₂]ZrCl₂ ( 2 ), and [Me₂Si(Me₄Cp)^tBuN]TiCl₂ ( 3 ) in the presence of MAO by terpolymerizing different amounts of 5‐vinyl‐2‐norbornene with constant amounts of ethylene and norbornene at 60°C. The highest cycloolefin incorporations and highest activity in terpolymerizations were achieved with 1 . The distribution of the monomers in the terpolymer chain was determined by NMR spectroscopy. As confirmed by XRD and DSC analysis, catalysts 1 and 3 produced amorphous terpolymer, whereas 2 yielded terpolymer with crystalline fragments of long ethylene sequences. When compared with poly‐(ethylene‐co‐norbornene), VNB increased both the glass transition temperatures and molar masses of terpolymers produced with the constrained geometry catalyst whereas decreased those for the metallocenes.     

Copolymerization of norbornene with methoxycarbonylnorbornene catalyzed by Ni{CF3C(O)CHC[N(naphthyl)]CH3}2/B(C6F5)3 catalytic system and good processability for Dry/Wet phase inversion and electrospinning technique

Copolymerization of norbornene (NB) with methoxycarbonylnorbornene (NB‐COOCH₃) was carried out with catalytic system of Ni{CF₃C(O)CHC[N(naphthyl)]CH₃}₂ and B(C₆F₅)₃ in toluene. The catalytic system exhibited higher activity 2.69 × 10⁵ (gpolymer/mol Ni h) for copolymerization of norbornene and methoxycarbonylnorbornene. The influence results of the comonomer feed content on the polymerization showed that the NB‐COOCH₃ has a very high insertion ratio in all copolymers, and the NB‐COOCH₃ content in copolymers can be controlled to be 7.9–77.6 mol % at content of 10–90 mol % of the NB‐COOCH₃ in the monomer feeds ratios. The reactivity ratios, r_NB‐COOCH3 = 0.578 and r_NB = 0.859, were determined by the Kelen–TÜdÕs method. Copolymers were processed by solution casting method, dry/wet phase inversion technique, and electrospinning. The films prepared by solution casting method showed good transparency in the visible region. The membranes processed by dry/wet phase inversion technique were microporous structures. The fibers diameters fabricated by electrospinning were about 3 μm. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Living regioselective copolymerization of ethylene with nonconjugated bicyclic dienes using (salicylaldiminato)(β‐enaminoketonato) titanium catalysts

A series of heteroligated (salicylaldiminato)(β‐enaminoketonato)titanium complexes [3‐^tBu‐2‐OC₆H₃CH?N(C₆F₅)] [PhN?C(CF₃)CHCRO]TiCl₂ [ 3a : R = Ph, 3b : R = C₆H₄Cl(p), 3c : R = C₆H₄OMe(p), 3d : R = C₆H₄Me(p), 3e : R = C₆H₄Me(o)] were synthesized and characterized. Molecular structures of 3b and 3c were further confirmed by X‐ray crystallographic analyses. In the presence of modified methylaluminoxane as a cocatalyst, these unsymmetric catalysts displayed favorable ability to incorporate 5‐vinyl‐2‐norbornene (VNB) and 5‐ethylidene‐2‐norbornene (ENB) into the polymer chains, affording high‐molecular weight copolymers with high‐comonomer incorporations and alternating sequence under the mild conditions. The comonomer concentration in the polymerization medium had a profound influence on the molecular weight distribution of the resultant copolymer. At initial comonomer concentration of higher than 0.4 mol/L, the titanium complexes with electron‐donating groups in the β‐enaminoketonato moiety mediated room‐temperature living ethylene/VNB or ENB copolymerizations. Polymerization results coupled with density functional theory calculations suggested that the highly controlled living copolymerization is probably a consequence of the difficulty in chain transfer of VNB (or ENB)‐last‐inserted species and some characteristics of living ethylene polymerization under limited conditions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Kinetics and mechanism of the addition of the phthalimid-n-oxyl radical to the double bond of vinyl compounds

The kinetics of the decomposition of the phthalimid-N-oxyl radical (PINO) in acetic acid has been studied. The rate constants of the addition of the radical to T bonds of molecules of vinyl compounds – styrene, methyl methacrylate, acrylonitrile, and methyl acrylate – have been measured. It was shown that electron-donor substituents in the monomer molecule increase, while electron-acceptor substituents decrease the rate of addition. The reactivity of monomers in the elementary step of addition of the PINO radical decreases in the order CH₂=C(CH₃)C₆H₅ > CH₂=CHC₆H₅ > CH₂=C(CH₃)COOCH₃ > CH₂=CHCOOCH₃ > CH₂=CHCN.     

Cationic polymerization of vinyl ether with a benzoate pendant: The formation of long‐lived polymers and the identification of side reactions

The cationic polymerization of 2‐[4‐(methoxycarbonyl)phenoxy] ethyl vinyl ether, a vinyl ether with a benzoate pendant, was carried out with an HCl/ZnCl₂ initiating system in methylene chloride at −15 °C. The polymerization proceeded with living/long‐lived propagating species to produce polymers with controlled molecular weights and relatively narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight ≤ ∼1.4), despite the formation of a small amount of oligomeric products during the polymerization. The structural analysis showed that the lowest molecular weight oligomer had the structure CH₃CH(OCH₂CH₂OC₆H₄COOCH₃)OCH₂CH₂OC₆H₄COOCH₃. The oligomer was formed by the reaction of the monomeric propagating species with the alcohol produced by the side reaction of the active species with water as an impurity during the early stage of polymerization. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4362–4372, 2000     

Polyolefins with high glass transition temperatures

The copolymerization of propene and norbornene with the isospecific metallocene catalyst dimethylsilylenebis(η⁵-inden-1-yl)zirconium dichloride/methylaluminoxane ((CH₃)₂Si[Ind]₂ZrCl₂/MAO) was investigated. Because of the surprisingly high reactivity of the cyclic olefin copolymers with a norbornene content of 11 mol-% up to 98 mol-% were synthesized. The resulting copolymers are amorphous. The glass transition temperatures studied by differential scanning calorimetry measurements increase with rising norbornene content in the copolymer. High glass transition temperatures of T_g > 240°C were found for the copolymers with the highest content of norbornene.     

Copolymerization of Propene and 5‐Vinyl‐2‐Norbornene: A Simple Route to Polar Poly(propylene)s

Summary: The metallocenes rac‐C₂H₄(Ind)₂ZrCl₂ ( 1 ), rac‐Me₂Si(Ind)₂ZrCl₂ ( 2 ), and rac‐Me₂Si(2‐Me‐benz[e]Ind)₂ZrCl₂ ( 3 ) efficiently copolymerize propene and 5‐vinyl‐2‐norbornene (VNB). 1 and 2 give a high VNB content and high productivities, whereas 3 gives moderate incorporation. Surprisingly, precatalysts 1 and 2 , which have very closely related structures, showed very different reactivities toward VNB, with 1 having a greater affinity for VNB than for propene. The copolymers are quantitatively converted into polyolefins with polar functionalities.

     

Pd(II) complexes bearing di‐ and monochelate fluorinated β‐ketonaphthyliminato ligand and their catalytic properties towards vinyl‐addition polymerization and copolymerization of norbornene and ester‐functionalized norbornene derivative

Fluorinated β‐ketonaphthyliminate ligand CF₃C(O)CHC[HN(naphthyl)]CH₃ ( L1 ) and Pd(II) complexes with dichelate fluorinated β‐ketonaphthyliminato ligand, {CF₃C(O)CHC[N(naphthyl)]CH₃}₂Pd ( C1 ), as well as with monochelate fluorinated β‐ketonaphthyliminato ligand, {CF₃C(O)CHC[N(naphthyl)]CH₃}Pd(CH₃)(PPh₃) ( C2 ), were synthesized and their solid‐state structures were confirmed using X‐ray crystallographic analysis. The Pd(II) complexes were employed as precursors to catalyze norbornene (NB) homo‐ and copolymerization with ester‐functionalized NB derivative using B(C₆F₅)₃ as a co‐catalyst. High activity up to 2.3 × 10⁵ g_polymer mol_Pd^?1 h^?1 for the C1 /B(C₆F₅)₃ system and 3.4 × 10⁶ g_polymer mol_Pd^?1 h^?1 for the C2 /B(C₆F₅)₃ system was exhibited in NB homopolymerization. Moreover, the Pd(II) complexes exhibited a high level of tolerance towards the ester‐functionalized MB monomer. In comparison with the C1 /B(C₆F₅)₃ system, the C2 /B(C₆F₅)₃ system exhibited better catalytic property towards the copolymerization of NB with 5‐norbornene‐2‐carboxylic acid methyl ester (NB‐COOCH₃), and soluble vinyl‐addition‐type copolymers were obtained with relatively high molecular weights (3.6 × 10⁴–7.5 × 10⁴ g mol^?1) as well as narrow molecular weight distributions (1.49–2.15) depending on the variation of monomer feed ratios. The NB‐COOCH₃ insertion ratio in all copolymers could be controlled in the range 2.8–21.0 mol% by tuning a content of 10–50 mol% NB‐COOCH₃ in the monomer feed ratios. Copolymerization kinetics were expressed by the NB and NB‐COOCH₃ monomer reactivity ratios: r_NB‐COOCH3 = 0.18, r_NB = 1.28 were determined for the C1 /B(C₆F₅)₃ system and r_NB‐COOCH3 = 0.19, r_NB = 3.57 for the C2 /B(C₆F₅)₃ system using the Kelen–Tüdõs method. Copyright © 2014 John Wiley & Sons, Ltd.     

Thiol–norbornene materials: Approaches to develop high Tg thiol–ene polymers

The ability to prepare high T_g low shrinkage thiol–ene materials is attractive for applications such as coatings and dental restoratives. However, thiol and nonacrylated vinyl materials typically consist of a flexible backbone, limiting the utility of these polymers. Hence, it is of importance to synthesize and investigate thiol and vinyl materials of varying backbone chemistry and stiffness. Here, we investigate the effect of backbone chemistry and functionality of norbornene resins on polymerization kinetics and glass transition temperature (T_g) for several thiol–norbornene materials. Results indicate that T_gs as high as 94 °C are achievable in thiol–norbornene resins of appropriately controlled chemistry. Furthermore, both the backbone chemistry and the norbornene moiety are important factors in the development of high T_g materials. In particular, as much as a 70 °C increase in T_g was observed in a norbornene–thiol specimen when compared with a sample prepared using allyl ether monomer of analogous backbone chemistry. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5686–5696, 2007     

Homo‐ and copolymerization of ethylene and norbornene with bis(β‐diketiminato) titanium complexes activated with methylaluminoxane

Homo‐ and copolymerization of ethylene and norbornene were investigated with bis(β‐diketiminato) titanium complexes [ArNC(CR₃)CHC(CR₃)NAr]₂TiCl₂ (R = F, Ar = 2,6‐diisopropylphenyl 2a; R = F, Ar = 2,6‐dimethylphenyl 2b ; R = H, Ar = 2,6‐diisopropylphenyl 2c ; R = H, Ar = 2,6‐dimethylphenyl 2d) in the presence of methylaluminoxane (MAO). The influence of steric and electric effects of complexes on catalytic activity was evaluated. With MAO as cocatalyst, complexes 2a–d are moderately active catalysts for ethylene polymerization producing high‐molecular weight polyethylenes bearing linear structures, but low active catalysts for norbornene polymerization. Moreover, 2a – d are also active ethylene–norbornene (E–N) copolymerization catalysts. The incorporation of norbornene in the E–N copolymer could be controlled by varying the charged norbornene. ¹³C NMR analyses showed the microstructures of the E–N copolymers were predominantly alternated and isolated norbornene units in copolymer, dyad, and triad sequences of norbornene were detected in the E–N copolymers with high incorporated content of norbornene. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 93–101, 2008     

Synthesis and characterization of materials prepared via the copolymerization of ethylene with 1‐octadecene and norbornene using a [(π‐cyano‐nacnac)Cp] zirconium complex

[3‐Cyano‐2‐(2,6‐diisopropylphenyl)aminopent‐2‐en‐4‐(phenylimine)tris (pentafluorophenyl)borate](η⁵‐C₅H₅)ZrCl₂, [(B(C₆F₅)₃‐ NC‐nacnac)CpZrCl₂], precatalyst ( 2 ) can be treated with low concentrations of methylaluminoxane (MAO) to generate active sites capable of copolymerizing ethylene with 1‐octadecene or norbornene under mild conditions. A series of poly(ethylene‐co‐octadecene) and poly(ethylene‐co‐norbornene) copolymers were prepared, and their properties were characterized by NMR, differential scanning calorimetry, and mechanical analysis. The results show that this system produced poly(ethylene‐co‐octadecene) copolymers with a branching content of about 8 mol %. However, upon increasing the comonomer concentration, a drastic reduction in the M_n of the product is observed concomitant with an increase in comonomer incorporation. This leads to a gradual decrease in Young's modulus and stress at break, indicating an increase in the “softness” of the copolymer. In the case of copolymerizations of ethylene and norbornene, the catalytic system ( 2 /MAO) shows a substantial decrease in reactivity in the presence of norbornene and generates copolymer chains in which 5–10 mol % norbornene is in blocks. We also observe that ethylene norbornene copolymers exhibit a high degree of alternating insertions (close to 50%), as determined by NMR spectroscopy. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Catalytic Consequences of the Thermodynamic Activities at Metal Cluster Surfaces and Their Periodic Reactivity Trend for Methanol Oxidation

The periodic reactivity trend and the connection of kinetics to the thermodynamic activity of oxygen are established for the oxidation of methanol on metal clusters. First‐order rate coefficients are a single‐valued function of the O₂‐to‐CH₃OH ratio, because this ratio, together with the rate constants for O₂ and CH₃OH activation, determine the oxygen chemical potential, thus the relative abundance of active sites and bulk chemical state of the clusters. CH₃OH activation rate constants on oxygen‐covered Ag, Pt, and Pd and on RuO₂ clusters vary with the metal–oxygen binding strength in a classical volcano‐type relation, because the oxygen‐binding strength directly influences the reactivities of oxygen as H abstractors during the kinetically relevant CH₃OH activation step. The differences in oxygen thermodynamic activity lead to five orders of magnitude variation in rates (Pt>Pd>RuO₂>Ag, 373 K), because of its strong effects on the activation enthalpy and more prominently activation entropy in CH₃OH activation.     

Chain-transfer constant of fluoroalcohols

Chain transfer constants of some fluoroalcohols [HCF₂(CF₂)_n?1CH₂OH, n = 2, 4, 6] in the catalyzed polymerization of vinyl acetate, styrene, acrylonitrile, and methyl methacrylate at 60°C have been evaluated by a method based on degree of polymerization. Since fluoroalcohols are normally nonsolvents for polymers, a homogeneous reaction phase is maintained by carrying out the polymerization in benzene (except in case of acrylonitrile, where no solvent was used). The transfer constants vary, depending on the reactivity as well as the polarity of the radicals, in the following order: vinyl acetate > styrene > methyl methacrylate > acrylonitrile. Of the three fluoroalcohols studied, the transfer constants increase with the increasing value of n. The results have been interpreted in terms of polar structure contribution in the transition state of the transfer reactions.     

2-Benzoimidazol-8-alkylquinolinylnickel(II) complexes as efficient catalysts for ethylene oligomerization and vinyl polymerization of norbornene

A series of nickel complexes LNiCl₂ (C1–C16), where L represents 2-benzoimidazol-8-alkylquinoline and its derivatives, were prepared as potential catalysts for the oligomerization of ethylene. The molecular structure of a representative complex C2·CH₃CH₂OH was determined by single-crystal X-ray diffraction. Upon treatment with diethylaluminium chloride (Et₂AlCl), all nickel complex pre-catalysts exhibited good activities in the oligomerization of ethylene. Furthermore, in the presence of methylaluminoxane (MAO), the nickel pre-catalysts were suitable for vinyl polymerization of norbornene.     

Preparation of Polar Ethylene–Norbornene Copolymers by Metallocene Terpolymerization with Triisobutylaluminium‐Protected But‐3‐en‐1‐ol

But‐3‐en‐1‐ol has been pre‐protected by triisobutylaluminium and terpolymerized with ethylene and norbornene by rac‐[Et(Ind)₂]ZrCl₂/MAO catalysts. The strong polarity of diisobutyl(but‐3‐en‐1‐oxy)aluminum causes a slight reduction in the catalyst activity and yields a small fraction of crystallinity. The but‐3‐en‐1‐ol content in the terpolymer is as high as 3.2% and can be readily adjusted by varying the reaction conditions. When the norbornene/ethylene ratio is over 10, the norbornene incorporation efficiency is not affected by the polar monomer and is close to that of the copolymerization. Similar to the ethylene/norbornene copolymers, the thermal properties of the obtained terpolymers are mainly determined by their norbornene contents.

     

Ni(II) and Pd(II) complexes bearing benzocyclohexane–ketoarylimine for copolymerization of norbornene with 5‐norbornene‐2‐carboxylic ester

A serial of late transition metal complexes, which bearing Benzocyclohexane–ketoarylimine ligand and named as Mt(benzocyclohexane–ketoarylimino)₂ {Mt(bchkai)₂: Mt=Ni or Pd; bchkai=C₁₀H₈(O)CN(Ar)CH₃; Ar=naphthyl or fluoryl}, have been synthesized and characterized. The molecular structures of the ligands and nickel complex have been confirmed by X‐ray single‐crystal analyses. The nickel complexes exhibited very high activity up to 2.7 × 10⁵ g_polymer/mol_Ni·h and palladium complexes showed high activity up to 2.3 × 10⁵ g_polymer/mol_Pd·h for norbornene (NB) homo‐polymerization with tris(pentafluorophenyl)borane as cocatalyst. The four complexes were effective for copolymerization of NB and 5‐norbornene‐2‐carboxylic acid methyl ester (NB‐COOCH₃) in relatively high activities (0.1–2.4 × 10⁵ g_polymer/mol_Mt·h) and produced the addition‐type copolymers with relatively high molecular weights (0.5 × 10⁵–1.2 × 10⁵ g/mol) as well as narrow molecular weight distributions (PDI < 2 for all polymers). Influences of the metals and comonomer feed content on the polymerization activity as well as on the incorporation rates (20.9–42.6%) were investigated. The achieved NB/NB‐COOCH₃ copolymers were confirmed to be noncrystalline, exhibited good thermal stability (T_d > 400°C) and showed good solubility in common organic solvents. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Initiation reactivity of anionic polymerization of fluorinated acrylates and methacrylates with diethyl(ethyl cyanoacetato)aluminum

Pseudo first‐order rate constants of the reaction of diethyl(ethyl cyanoacetato)aluminum [(C₂H₅)₂Al(NCCHCOOC₂H₅)] with 17 fluorinated acrylates and methacrylates and five hydrocarbon analogs for references were investigated to examine the initiation reactivities of the anionic polymerization of fluorinated vinyl monomers to afford the reactivity order: CH₂?C(CF₃)COOC₂H₅ > CH₂?C(CF₃)COOCH(CH₃)₂ > CH₂?CHCOOCH₂C₆F₅ > CH₂?C(CF₃)COOC(CH₃)₃ > CH₂?C(CF₃)COOCH₂C₆F₅ > CH₂?C(CF₃)COOCH(CF₃)₂ ≥ CH₂?CHCOOCH₃ > CH₂?CHCOOCH₂C₆H₅ ≥ CH₂?C(CF₃)COOCH₂CF₃ > CH₂?C(CH₃)COOCH₂C₆F₅ > CH₂?CHCOOCH₂CF₃ > CH₂?CHCOOCH₂C₂F₅ > CH₂?CHCOOCH(CF₃)₂ > CH₂?C(CH₃)COOCH₃ > CH₂?C(CH₃)COOCH₂C₆H₅ ≥ CH₂?C(CH₃)COOCH₂CH₂C₈F₁₇ > CH₂?C(CH₃)COOCH(CH₃)₂ > CH₂?C(CH₃)COOCH₂C₂F₅ ≥ CH₂?C(CH₃)COOCH₂CF₃. No rate constants for CH₂?C(CH₃)COOCH(CF₃)₂, CH₂?CFCOOC(CH₃)₃, and CH₂?CFCOOCH₂C₂F₅ were obtained because of too fast polymerization. The incorporation of a trifluoromethyl group into the vinyl group enhanced the reactivity toward the delocalized carbanion. The reactivity of other fluorinated acrylates and methacrylates was concluded to approximately be controlled by the fluorine contents and the bulkiness of substituents of monomers. The reactivity was generally decreased by increasing fluorine contents of fluoroalkyl substituents in ester groups. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7011–7021, 2008     

Highly active ethylene polymerization and copolymerization with norbornene using bis(imino‐indolide) titanium dichloride–MAO system

A catalytic system of new titanium complexes with methylaluminoxane (MAO) was found to effectively polymerize ethylene for high molecular weight polyethylene as well as highly active copolymerization of ethylene and norbornene. The bis (imino‐indolide)titanium dichlorides (L₂TiCl₂, 1 – 5 ), were prepared by the reaction of N‐((3‐chloro‐1H‐indol‐2‐yl)methylene)benzenamines with TiCl₄, and characterized by elemental analysis, ¹H and ¹³C NMR spectroscopy. The solid‐state structures of 1 and 4 were determined by X‐ray diffraction analysis to reveal the six‐coordinated distorted octahedral geometry around the titanium atom with a pair of chlorides and ligands in cis‐forms. Upon activation by MAO, the complexes showed high activity for homopolymerization of ethylene and copolymerization of ethylene and norbornene. A positive “comonomer effect” was observed for copolymerization of ethylene and norbornene. Both experimental observations and paired interaction orbital (PIO) calculations indicated that the titanium complexes with electron‐withdrawing groups in ligands performed higher catalytic activities than those possessing electron‐donating groups. Relying on different complexes and reaction conditions, the resultant polyethylenes had the molecular weights M_w in the range of 200–2800 kg/mol. The influences on both catalytic activity and polyethylene molecular weights have been carefully checked with the nature of complexes and reaction conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3415–3430, 2007     

Mechanism of radiation-induced degradation of poly(methyl methacrylate) as studied by ESR and electron spin echo methods

The role of radical species in the degradation of poly(methyl methacrylate) (PMMA) induced by γ-irradiation has been studied by means of electron spin resonance and electron spin echo spectroscopy. The major radical species generated initially at 77 K are assigned to main chain ? CH ? and side chain ? COOCH₂ radicals, and ? COOCH anion radical. Only the ? COOCH₂ radical converts to the scission-type ? CH₂ ? C(CH₃)COOCH₃ radical on warming the sample of >180 K. A part of the ? CH ? radical disappears on warming the sample of >265 K. It is concluded that the scission of PMMA main chain occurs by the intramolecular process from the ? COOCH₂ radical as the precursor state.     

Photobase generation from amineimide derivatives and their use for curing an epoxide/thiol system

The structural effects of amineimide derivatives on photobase generation and the use of the resultant base for thermal curing of an epoxide/thiol system are investigated. The results of UV spectral change and gas chromatographic‐mass spectrometric analysis indicated that amineimide derivatives undergo photolysis by UV irradiation and generate bases. The order of conversion of the photolysis for the functional groups introduced to amineimide derivatives was NO₂ > N(CH₃)₂ > CN > OCH₃ > H. By using aminimide derivatives with NO₂ and N(CH₃)₂ groups, the curing of the epoxide/thiol system was shifted to lower temperature after UV irradiation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4045–4052, 2002