Synthesis and characterization of norbornene–ethylene–styrene terpolymers with a substituted ansa‐fluorenylamidodimethyltitanium‐based catalyst

This article reports a synthetic method for a norbornene–ethylene–styrene (N‐E‐S) terpolymer, which has not been well investigated so far, via incorporation of styrene (S) into vinyl‐type norbornene–ethylene (N‐E) copolymers catalyzed by a substituted ansa‐fluorenylamidodimethyltitanium [Me₂Si(3,6‐tBu₂Flu)(tBuN)]TiMe₂ catalyst ( I ) activated with a [Ph₃C][B(C₆F₅)₄]/Al(iBu)₃ cocatalyst at room temperature in toluene. The resulting terpolymerization product contained the targeted N‐E‐S terpolymer and the contaminated homopolymers, which were then able to be completely removed by solvent fractionation techniques. While homopolystyrene was easily extracted by fractionation with methylethylketone as a soluble part, homopolyethylene and a trace amount of homopolynorbornene could be perfectly separated by fractionation with chloroform as insoluble parts. The detail characterizations of a chloroform‐soluble polymer with gel permeation chromatography, nuclear magnetic resonance, and differential scanning calorimetry analyses proved that it contained a true N‐E‐S terpolymer with long N‐E sequences incorporated with isolated or short styrene sequences. The homogeneity of the morphology together with a single glass transition temperature that proportionally decreased with the increase of the styrene contents indicated that the N‐E‐S terpolymer obtained in this work is a random polymer with an amorphous structure. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2765–2773, 2007     

Synthesis of highly thermostable norbornene‐isoprene‐1‐octene terpolymer with titanium catalyst

Terpolymerization of norbornene (NB), isoprene (IP), and 1‐octene was achieved by using fluorenylamido‐ligated titanium catalyst, which showed very high activity for the copolymerization of NB and various α‐olefins. The content of IP in the terpolymer was controlled by the feed ratio and reaction temperature up to 7 mol %. The incorporated IP was mainly inserted in 1,4‐addition. The polymer was dissolved into common solvents such as toluene and chloroform, which enabled the preparation of a transparent film by solution casting process. The degradation temperature of the terpolymer was comparable with other cyclic olefin copolymers and the glass transition temperature (T_g) was higher than that of NB‐1‐octene copolymer with almost the same NB content. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2136–2140     

Homo‐ and copolymerization of norbornene derivatives with ethene by ansa‐fluorenylamidodimethyltitanium activated with methylaluminoxane

(t‐BuNSiMe₂Flu)TiMe₂ ( 1 ) activated with Me₃Al‐free methylaluminoxane (dried MAO) which conducts vinyl addition polymerization of norbornene (N) with very high activity was applied for homopolymerization of N derivatives (i.e., 5‐vinyl‐2‐norbornene (5V2N), 5‐ethylidene‐2‐norbornene (5E2N), dicyclopentadiene (DCPD)) at 40 °C. The activities for the N derivatives were about two orders of magnitude lower than that for N and decreased in the following order: 5E2N ? 5V2N ? DCPD. Copolymerization of ethene (E) and 5E2N under an atmospheric pressure of E was then conducted by 1 ‐dried MAO. The copolymerization proceeded with better activity than the homopolymerization of 5E2N and gave poly(E‐co‐5E2N) with narrow molecular weight distribution. The content of the ethylidene group in poly(E‐co‐5E2N) was controlled by the feed ratio of 5E2N/E. The T_g value of the copolymer changed from 70 °C to 155 °C according to the 5E2N content from 27 mol % to 68 mol %. The addition of N as a third monomer to the E‐5E2N copolymerization improved the activity and raised the T_g values of the terpolymer above 200 °C. The content of 5E2N was controlled by the 5E2N/N ratio with keeping the high T_g values. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4581–4587, 2007     

Composition distribution of ethylene or propylene–norbornene copolymers obtained with zirconocene catalysts

Copolymerization of ethylene or propylene and norbornene (NB) was carried out with stereospecific zirconocene catalysts rac‐ethylenebis(indenyl)zirconium dichloride, rac‐dimethylsilylenebis(indenyl)zirconium dichloride ( 2 ), rac‐dimethylsilylenebis(2‐methylindenyl)zirconium dichloride, and diphenylmethylene(cyclopentadienyl)(9‐fluorenyl)zirconium dichloride combined with cocatalysts at 40 °C. Temperature‐rising elution fractionation of the copolymers was carried out with cross‐fractionation chromatography with o‐dichlorobenzene as a solvent, and a broad distribution of the copolymer composition was detected. The fraction eluted at lower temperature contained higher NB. The effect of the polymerization time was examined in the ethylene–NB copolymerization with catalyst 2 , and the higher‐temperature elution fraction increased with increasing polymerization time. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 441–448, 2003     

Functionalization of vinylic addition polynorbornenes via efficient copolymerization of norbornene using Ni(II)‐Me complexes

The facile and efficient functionalization of polynorbornene has been achieved through direct copolymerization of norbornene (NB) with 5‐norbornene‐2‐yl acetate (NBA) or 5‐norbornene‐2‐methanol (NBM) using a series of β‐ketiminato Ni(II)‐Me pyridine complexes 1–4 (Scheme 2 ) in the presence of B(C₆F₅)₃. Remarkably, the monomer conversion could reach up to about 96% in 10 min in the NB/NBA copolymerization. The copolymers with wide NBA contents (3.3–38.4 mol %) were obtained by variation of reaction conditions. These copolymers have high molecular weights (MWs) (M_n = 41.8–144 kg/mol) and narrow MW distributions (M_w/M_n = 1.80–2.27). In the absence of alkyl aluminum compounds, a monomer conversion of 81% was observed in the NB/NBM copolymerization, and copolymers with NBM content in the range of 11.2–21.8 mol % were obtained by variation of reaction conditions. In addition, Ni(II)‐Me pyridine complexes 2 was very active at a low B/Ni molar ratio of 6, while bis‐ligand complex 6 bearing the same ligand just showed moderate efficiency at a high B/Ni molar ratio of 20. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Investigation of the radical copolymerization and terpolymerization of maleic anhydride and norbornenes by an in situ 1H NMR analysis of kinetics and by the mercury method: Evidence for the lack of charge‐transfer‐complex propagation

The radical copolymerization of electron‐deficient maleic anhydride (MA) and electron‐rich norbornene (NB) derivatives with 2,2′‐azobis(isobutyronitrile) (AIBN) in dioxane‐d₈ has been monitored in situ by ¹H NMR spectroscopy with free induction decays recorded every 30 min at 60, 70, or 84 °C. The ratios of the monomer pairs were varied in some cases. The NB derivatives employed in this study included bicyclo[2.2.1]hept‐2‐ene (NB), t‐butyl 5‐norbornene‐2‐carboxylate, methyl 5‐norbornene‐2‐methyl‐2‐carboxylate, and ethyl tetracyclo[4.4.0.1^2,5.1^7,10]dodec‐3‐ene‐8‐carboxylate. Decomposition of AIBN, consumption of the monomers, feed ratios, endo/exo ratios, copolymer compositions, and copolymer yields were studied as a function of polymerization time. Furthermore, a homopolymerizable third monomer (t‐butyl methacrylate, methacrylic acid, t‐butyl acrylate, or acrylic acid) was added to the NB/MA 1/1 system, revealing that the methacrylic monomer polymerizes rapidly in the early stage and that the ratio of MA to NB in the terpolymer strongly deviates from 1/1. In contrast, however, the acrylic monomers are more uniformly incorporated into the polymer. Nevertheless, these studies indicate that MA and NB do not always behave as a pair in radical polymerization and disproves the commonly believed charge‐transfer mechanism. Electron‐deficient fumaronitrile was also included in the kinetics study. To further understand the copolymerization mechanism, MA and NB were competitively reacted with a cyclohexyl radical generated by the treatment of cyclohexylmercuric chloride with sodium borohydride (mercury method). A gas chromatographic analysis of the reaction mixtures has revealed that a cyclohexyl radical reacts with MA almost exclusively in competition and that the cyclohexyl adduct of MA essentially accounts for all the products in a mass balance experiment, eliminating a possibility of the formation of an adduct involving the MA–NB charge‐transfer complex. Thus, the participation of a charge‐transfer complex in the copolymerization of MA and NB cannot be important. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3521–3542, 2000     

Synthesis and characterization of ethylene‐propylene‐1‐pentene terpolymers

Ethylene (E), propylene (P), and 1‐pentene (A) terpolymers differing in monomer composition ratio were produced, using the metallocenes rac‐ethylene bis(indenyl) zirconium dichloride/methylaluminoxane (rac‐Et(Ind)₂ZrCl₂/MAO), isopropyl bis(cyclopentadienyl)fluorenyl zirconium dichloride/methylaluminoxane (Me₂C(Cp)(Flu)ZrCl₂/MAO, and bis(cyclopentadienyl)zirconium dichloride, supported on silica impregnated with MAO (Cp₂ZrCl₂/MAO/SiO₂/MAO) as catalytic systems. The catalytic activities at 25 °C and normal pressure were compared. The best result was obtained with the first catalyst. A detailed study of ¹³C NMR chemical shifts, triad sequences distributions, monomer‐average sequence lengths, and reactivity ratios for the terpolymers is presented. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 947–957, 2008     

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     

Norbornene‐functionalized PEO‐b‐PCL: A versatile platform for mikto‐arm star,umbrella‐like,and comb‐like graft copolymers

Well‐defined in‐chain norbornene‐functionalized poly(ethylene oxide)‐b‐poly(?‐caprolactone) copolymers (NB‐PEO‐b‐PCL) were synthesized from a dual clickable containing both hydroxyl‐ and alkyne‐reactive groups, namely heterofunctional norbornene 3‐exo‐(2‐exo‐(hydroxymethyl)norborn‐5‐enyl)methyl hexynoate. A range of NB‐PEO‐b‐PCL copolymers were obtained using a combination of orthogonal organocatalyzed ring‐opening polymerization (ROP) and click copper‐catalyzed azide–alkyne cycloaddition (CuAAC). Ring‐opening metathesis polymerization (ROMP) of NB‐PEO‐b‐PCL macromonomers using ruthenium‐based Grubbs’ catalysts provides comb‐like and umbrella‐like graft copolymers bearing both PEO and PCL grafts on each monomer unit. Mikto‐arm star A₂B₂ copolymers were obtained through a new strategy based on thiol–norbornene photoinitiated click chemistry between 1,3‐propanedithiol and NB‐PEO‐b‐PCL. The results demonstrate that in‐chain NB‐PEO‐b‐PCL copolymers can be used as a platform to prepare mikto‐arm star, umbrella‐, and comb‐like graft copolymers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 4051–4061     

Radiochemical aging of ethylene–propylene–diene monomer elastomers. I. Mechanism of degradation under inert atmosphere

This article is devoted to the study of electron‐beam‐induced degradation under argon atmosphere of an ethylene–propylene–diene monomer (EPDM, based on 5‐ethylidene 2‐norbornene) and an ethylene–propylene rubber (EPR) containing the same molar ratio of ethylene/propylene. The chemical structure modifications of polymeric samples were analyzed by ultraviolet–visible and IR spectroscopies. Crosslinking reactions were deduced by measuring the changes in gel fraction and the degree of swelling in n‐heptane. Irradiation of EPDM and EPR created trans‐vinylene, vinyl, vinylidene, and dienic‐type unsaturations. The radiochemical yields for unsaturation formations in EPDM and EPR were similar. Degradation also involved crosslinking and the production of molecular hydrogen. The comparison between EPDM and EPR showed that the diene (in which a double bond is consumed with a high radiochemical yield) contributes to the increase in rate and intermolecular bridges density. Mechanisms are proposed to account for the main routes of EPDM degradation. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1239–1248, 2004     

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.     

A non‐PFT (polymerization filling technique) approach to poly(ethylene‐co‐norbornene)/MWNTs nanocomposites by in situ copolymerization with scandium half‐sandwich catalyst

The in situ synthesis of ethylene‐co‐norbornene copolymers/multi‐walled carbon nanotubes (MWNTs) nanocomposites was achieved by rare‐earth half‐sandwich scandium precursor [Sc(η⁵‐C₅Me₄SiMe₃)(η¹‐CH₂SiMe₃)₂(THF)] (1) activated by [Ph₃C][B(C₆F₅)₄], through a non‐PFT (Polymerization Filling Technique) approach. MWNTs nanocomposites with low aluminum residue were obtained with excellent yields even though small amounts of triisobutylaluminium were needed as scavenger to prevent catalyst poisoning by MWNT impurities. MWNT bundles were disaggregated and highly coated with Poly(ethylene‐co‐norbornene) [P(E‐co‐N)] as revealed by transmission electron microscopy. Interestingly, P(E‐co‐N) copolymers showed T_g over 130 °C as well as norbornene content over 50 mol %; both values were higher than those obtained by the cationic active species in 1 /[Ph₃C][B(C₆F₅)₄]. A series of copolymerization reactions by 1 /[Ph₃C][B(C₆F₅)₄]/AlⁱBu₃ without MWNTs produced copolymers with the same unexpected features. The NMR analysis revealed the presence of rac‐ENNE and rac‐ENNNE sequences. Thus, AlⁱBu₃ changed the stereoirregular alternating copolymer microstructure produced by 1 /[Ph₃C][B(C₆F₅)₄]. We conclude that AlⁱBu₃ is not only a scavenger for CNT impurities, but it reacts with the THF ligand to give coordinatively unsaturated active species. Finally, P(E‐co‐N)/MWNT masterbatches were mixed with commercial TOPAS to produce cyclic olefin copolymer nanocomposites with excellent dispersion of filler. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5709–5719, 2009     

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     

Alternating,gradient, block,and block–gradient copolymers of ethylene and norbornene by Pd–Diimine‐Catalyzed “living” copolymerization

We demonstrate, in this article, the facile synthesis of a broad class of low‐polydispersity ethylene–norbornene (E–NB) copolymers having various controllable comonomer composition distributions, including gradient, alternating, diblock, triblock, and block–gradient, through “living”/quasiliving E–NB copolymerization facilitated with a single Pd – diimine catalyst ( 1 ). This synthesis benefits from two remarkable features of catalyst 1 , its high capability in NB incorporation and high versatility in rendering E–NB “living” copolymerization at various NB feed concentrations ([NB]₀) while under an ethylene pressure of 1 atm and at 15 °C. At higher [NB]₀ values between 0.42 and 0.64 M, E–NB copolymerization with 1 renders nearly perfect alternating copolymers. At lower [NB]₀ values (0.11–0.22 M), gradient copolymers yield due to gradual reduction in NB concentration, with the starting chain end containing primarily alternating segments and the finishing end being hyperbranched polyethylene segments. Through two‐stage or three‐stage “living” copolymerization with sequential NB feeding, diblock or triblock copolymers containing gradient block(s) have been designed. This work thus greatly expands the family of E–NB copolymers. All the copolymers have controllable molecular weight and relatively low polydispersity (with polydispersity index below 1.20). Most notably, some of the gradient and block–gradient copolymers have been found to exhibit the characteristic broad glass transitions as a result of their possession of broad composition distribution. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Appreciable norbornene incorporation in the copolymerization of ethylene/norbornene using titanium catalysts containing trianionic N[CH2CH(Ph)O]33− ligands

The newly synthesized 1‐TiCl (C₃ symmetric) and 2‐TiCl (C_s symmetric) precatalysts in combination with MAO polymerized ethylene, cyclic olefins, and copolymerized ethylene/norbornene in good yields. The catalyst with C₃ symmetry exhibits moderate catalytic activity and efficient norbornene incorporation for E/NBE copolymerization in the presence of MAO [activity = 360 kg polymer/(mol Ti h), ethylene 1 atm, NBE 5 mmol/mL, 10 min], affording poly(ethylene‐co‐NBE)s with high norbornene contents (42.0%) and the C_s symmetric catalyst showed an activity of 420 kg polymer/(mol Ti h), ethylene 1 atm, NBE 5 mmol/mL affording poly(ethylene‐co‐NBE)s with 33.0% norbornene content. The effect of monomer concentration at ambient temperature and constant Al/Ti ratio for the homo and copolymerization was studied in a detailed manner. We found that apart from the electronic environment around the metal center the steric environment provided by the symmetry of the catalyst systems has a considerable influence on the percentage of norbornene content of the copolymer obtained. We also found that with a given catalyst a variable clearly influencing the copolymer microstructure, hence also the copolymer properties, is the monomer concentration at a given feed ratio. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 444–452, 2008     

Living copolymerization of ethylene with norbornene by fluorinated enolato‐imine titanium catalyst

Complex [Ti(κ²‐N,O‐{2,6‐F₂C₆H₃N?C(Me)C(H) ?C(CF₃) O})₂Cl₂] ( 1 ) was evaluated as catalyst for living copolymerization of ethylene (E) with norbornene (N) upon activation with dried methylaluminoxane (d‐MAO) at temperatures between 25 and 90 °C. Copolymerization performed at different [N]/[E] feed ratios afforded stereoirregular alternating high molar mass P(E‐co‐N) with narrow molar mass distribution. The living nature of E‐co‐N copolymerization by 1 /d‐MAO was demonstrated by kinetics at 50 °C. This catalyst system was used for the synthesis of block copolymers such as polyethylene (PE)‐block‐P(E‐co‐N) with a crystalline PE block and an amorphous P(E‐co‐N) block as well as P(E‐co‐N)₁‐block‐P(E‐co‐N)₂, having different norbornene contents in the segments and thus having different T_g values. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Ni(II) and Pd(II) complexes bearing novel bis(β‐ketoamino) ligand and their catalytic activity toward copolymerization of norbornene and 5‐norbornene‐2‐yl acetate combined with B(C6F5)3

Two complexes Mt{C₁₀H₈(O)C[N(C₆H₅)]CH₃}₂ [Mt = Ni(II); Mt = Pd(II)] were synthesized, and the solid‐state structures of the complexes have been determined by single‐crystal X‐ray diffractions. Homopolymerization of norbornene (NB) and copolymerization of NB and 5‐norbornene‐2‐yl acetate (NB‐OCOCH₃) were carried out in toluene with both the two complexes mentioned above in combination with B(C₆F₅)₃. Both the catalytic systems exhibited high activity toward the homopolymerization of NB (as high as 2.7 × 10⁵ g_polymer/mol_Ni h, for Ni(II)/B(C₆F₅)₃ and 2.1 × 10⁵ g_polymer/mol_Pd h for Pd(II)/B(C₆F₅)₃, respectively.). Although the Pd(II)/B(C₆F₅)₃ shows very lower activity toward the copolymerization of NB with NB‐OCOCH₃, Ni(II)/B(C₆F₅)₃ shows a high activity and produces the addition‐type copolymer with relatively high molecular weights (MWs; 1.80–2.79 × 10⁵ g/mol) as well as narrow MW distribution (1.89–2.30). The NB‐OCOCH₃ content in the copolymers can be controlled up to 5.8–12.0% by varying the comonomer feed ratios from 10 to 50%. The copolymers exhibited high transparency, high glass transition temperature (T_g > 263.9 °C), better solubility, and mechanical properties compared with the homopolymer of NB. The reactivity ratios of the two monomers were determined to be r_NB‐OCOMe = 0.08, r_NB = 7.94 for Ni(II)/B(C₆F₅)₃ system, and r_NB‐OCOMe = 0.07, r_NB = 6.49, for Pd(II)/B(C₆F₅)₃ system by the Kelen‐Tüdõs method. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

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     

Ring‐opening metathesis polymerization of amino acid‐functionalized norbornene derivatives

Amino acid‐derived novel norbornene derivatives, N,N′‐(endo‐bicyclo[2.2.1] hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐alanine methyl ester (NBA), N,N′‐(endo‐bicyclo[2.2.1]hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐leucine methyl ester (NBL), N,N′‐(endo‐bicyclo[2.2.1]hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐phenylalanine methyl ester (NBF) were synthesized and polymerized using the Grubbs 2nd generation ruthenium (Ru) catalyst. Although NBA, NBL, and NBF did not undergo homopolymerization, they underwent copolymerization with norbornene (NB) to give the copolymers with M_n ranging from 5200 to 38,100. The maximum incorporation ratio of the amino acid‐based unit was 9%, and the cis contents of the main chain were 54–66%. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5337–5343, 2006     

Latent cationic palladium(II) phosphine carboxylate complexes for norbornene polymerization

The catalytic efficacy of trans‐[(R₃P)₂Pd(O₂CR′)(LB)][B(C₆F₅)₄] ( 1 ) (LB = Lewis base) and [(R₃P)₂Pd(κ²‐O,O‐O₂CR′)][B(C₆F₅)₄] ( 2 ) for mass polymerization of 5‐n‐butyl‐2‐norbornene (Butyl‐NB) was investigated. The nature of PR₃ and LB in 1 and 2 are the most critical components influencing catalytic activity/latency for the mass polymerization of Butyl‐NB. Further, it was shown that 1 is in general more latent than 2 in mass polymerization of Butyl‐NB. 5‐n‐Decyl‐2‐norbornene (Decyl‐NB) was subjected to solution polymerization in toluene at 63(±3) °C in the presence of several of the aforementioned palladium complexes as catalysts and the polymers obtained were characterized by gel permeation chromatography. Cationic trans‐[(R₃P)₂PdMe(MeCN)][B(C₆F₅)₄] [R = Cy ( 3a ), and ⁱPr ( 3b )] and trans‐[(R₃P)₂PdH (MeCN)][B(C₆F₅)₄] [R = Cy ( 4a ), and ⁱPr ( 4b )], possible products from thermolysis of trans‐[(R₃P)₂Pd(O₂CMe)(MeCN)][B(C₆F₅)₄] [R = Cy ( 1a ) and ⁱPr ( 1g )], as well as trans‐[(R₃P)₂Pd(η³‐C₃H₅)][B(C₆F₅)₄] [R = Cy ( 5a ), and ⁱPr ( 5b )], were also examined as catalysts for solution polymerization of Decyl‐NB. A maximum activity of 5360 kg/(molPd h) of 2a was achieved at a Decyl‐NB/Pd: 26,700 ratio which is slightly better than that achieved with 5a [activity: 5030 kg/(molPd h)] but far less compared with 4a [activity: 6110 kg/(molPd h)]. Polydispersity values indicate a single highly homogeneous character of the active catalyst species. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 103–110, 2009