Syndioselective propylene polymerization: Comparison of Me2C(Cp)(Flu)ZrMe2 with Et(Cp)(Flu)ZrMe2

The kinetics and stereochemical control of propylene polymerization initiated by syndiospecific isopropylidene(1-η⁵-cyclopentadienyl)(1-η⁵-fluorenyl)-dimethylzirconium–methyl aluminoxane (1/MAO) and (1-fluorenyl-2-cyclopentadienylethane)-dimethylzirconium–MAO (2/MAO) were investigated. The influence of MAO concentration and polymerization temperature (T_p) on polymerization kinetics and polypropylene properties, such as molecular weight, molecular weight distribution (MWD), and stereoselectivity, have been studied in detail. The activity of both catalytic systems is very sensitive to the concentration of MAO. The 1/MAO and 2/MAO catalysts record maximum activity when [Al]/[Zr] ratio is around 1300 and 2500, respectively. The activity and the degree of stereochemical control are also sensitive to T_p. The 2/MAO catalyst is much more thermally stable than 1/MAO catalyst; the former shows maximum activity at 80°C, whereas the latter shows maximum activity at 20°C. The cationic active species generated by 2/MAO is not so stereorigid as those by 1/MAO so that 2/MAO catalyst produces sPP of broad MWD (4.43–6.38) and low syndiospecificity at high T_p. When T_p is above 50°C, 2/MAO catalyst produces completely atactic polypropylene. The results of fractionation of sPP samples produced by 1/MAO and 2/MAO demonstrate that 1/MAO catalyst is characterized by uniform active sites, but 2/MAO is characterized by multiple active sites. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 973–983, 1998     

Poly(pent‐1‐ene) Synthesized with the Syndiospecific Catalyst i‐Pr(Cp)(9‐Flu)ZrCl2/MAO

1‐Pentene was polymerized with the syndiospecific catalyst system i‐PrC(Cp)(9‐fluorenyl)ZrCl₂/MAO. The molar mass of the resulting polymers depends strongly on the reaction temperature and decreases from M̄_w = 126 000 at 0°C to M̄_w = 46 000 at 100°C, but is more or less independent of the monomer and the MAO concentration. The influence of reaction temperature and concentrations of MAO and monomer on the type of end‐groups generated during the chain termination, as well as on the type of stereoerror, was investigated. The degree of tacticity was dependent on the polymerization temperature with [rrrr] > 0.99 at 0°C and [rrrr] = 0.75 at 100°C.     

Copolymerization and characterization of ethene–1‐hexene copolymers prepared by using the (Me5Cp)2ZrCl2–MAO catalyst system

It is demonstrated that the catalyst system bis(pentamethylcyclopentadienyl)‐zirconium dichloride (Me₅Cp)₂ZrCl₂–methylaluminoxane (MAO) is able to produce random copolymers of ethene and 1‐hexene. The 1‐hexene incorporation in the copolymers is extremely small. Even in the case of a molar ratio of [ethene] to [1‐hexene] of 1/20 in the monomer feed, only 1.4 mol % 1‐hexene are incorporated according to ¹³C nuclear magnetic resonance (NMR) spectra. Nevertheless, the physical properties of the random copolymers change significantly in this small range of 1‐hexene incorporation, from a high‐density polyethene to a linear low‐density polyethene. Thus, the melting temperature, the degree of crystallinity, the density and lamella thickness, and the long period of the alternating crystalline and amorphous regions decrease with increasing 1‐hexene content in the random copolymers. Blends of high‐density polyethene prepared with the system (Me₅Cp)₂ZrCl₂–MAO and an elastomeric random copolymer of ethene and 1‐hexene are phase‐separated and show good compatibility, as demonstrated by transmission electron microscopy. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 439–447, 1999     

Copolymerization of ethylene/α‐olefins over (2‐MeInd)2ZrCl2/MAO and (2‐BzInd)2ZrCl2/MAO systems

Ethylene homopolymerization and ethylene/α‐olefin copolymerization were carried out using unbridged and 2‐alkyl substituted bis(indenyl)zirconium dichloride complexes such as (2‐MeInd)₂ZrCl₂ and (2‐BzInd)₂ZrCl₂. Various concentrations of 1‐hexene, 1‐dodecene, and 1‐octadecene were used in order to find the effect of chain length of α‐olefins on the copolymerization behavior. In ethylene homopolymerization, catalytic activity increased at higher polymerization temperature, and (2‐MeInd)₂ZrCl₂ showed higher activity than (2‐BzInd)₂ZrCl₂. The increase of catalytic activity with addition of comonomer (the synergistic effect) was not observed except in the case of ethylene/1‐hexene copolymerization at 40°C. The monomer reactivity ratios of ethylene increased with the decrease of polymerization temperature, while those of α‐olefin showed the reverse trend. The two catalysts showed similar copolymerization reactivity ratios. (2‐MeInd)₂ZrCl₂ produced the copolymer with higher M_w than (2‐BzInd)₂ZrCl₂. The melting temperature and the crystallinity decreased drastically with the increase of the α‐olefin content but T_m as a function of weight fraction of the α‐olefins showed similar decreasing behavior. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 928–937, 2000     

Copolymerization of ethylene and 1-octadecene with the Cp2ZrCl2/MAO and Cp2HfCl2/MAO catalyst systems

Summary The comparison of the copolymers obtained with the Cp₂ZrCl₂/MAO and Cp₂HfCl₂/MAO catalyst systems showed that the catalyst having hafnocene was much more reactive towards 1-octadecene than zirconocene. The comonomer concentration had to be three times higher in the zirconocene copolymerization than in the hafnocene copolymerization when the level of 6 mol-% was reached. Although the hafnocene catalyst was more reactive towards 1-octadecene, the molecular weights were higher than in the copolymers obtained with the zirconocene catalyst.The total activity of the zirconocene was 10 times higher than with the hafnocene catalyst. With the zirconocene catalyst the activity towards ethylene was constantly increasing by increasing the comonomer concentration but stayed nearly constant with the hafnocene catalyst. It seemed that there is no rate enhancement effect upon comonomer addition with the hafnocene catalyst.     

Synthesis and properties of hybrid materials obtained by in situ copolymerization of ethylene and propylene in the presence of Al2O3 nanofibers (NafenTM) on catalytic system rac‐Et(2‐MeInd)2ZrMe2/isobutylalumoxane

Nanofibers of Al₂O₃ (commercial product Nafen^TM) with characteristic length of ～100 nm and diameter of ～10 nm were used to create new hybrid materials based on copolymer of ethylene and propylene. Nanocomposites were obtained by in situ catalytic copolymerization on the system rac‐Et(2‐MeInd)₂ZrMe₂/isobutylalumoxane. Formation of the nanocomposites with uniform distribution of Nafen nanoparticles in polymer matrix was confirmed by scanning and transmission electron microscopy. According to dynamic mechanical analysis data, introduction of the nanofiller in an amount of up to 3 wt % leads to an increase in glass transition temperature by 10 °C (E″) and by 21 °C (tan δ). The nanocomposites exhibit improved physico‐mechanical properties (tensile strength and elongation at break). It is shown that the nanofiller significantly improves resistance of the nanocomposite to the thermo‐oxidative and thermal degradation. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44678.     

Long Chain Branched Polypropene Prepared by Means of Propene Copolymerization with 1,7‐Octadiene Using MAO‐Activated rac‐Me2Si(2‐Me‐4‐Phenyl‐Ind)2ZrCl2

Small amounts of 1,7‐octadiene (OD) comonomer, ranging from 0.5–5.0 mol‐%, were added during propene polymerization, catalyzed with methylalumoxane (MAO) activated rac‐Me₂Si(2‐Me‐4‐phenyl‐Ind)₂ZrCl₂ (MPI), in order to incorporate long chain branches and small amounts of high molecular mass polypropene (PP), thus improving melt processability of isotactic metallocene‐polypropene. As a function of the OD content the PP melting temperatures varied from 120 to 160°C. The presence of long chain branches was reflected by increased zero shear viscosities combined with pronounced shear thinning behavior in the case of propene/OD copolymers with molecular mass distribution of M̄_w/M̄_n < 4. Rheological measurements clearly revealed crosslinking occurring at high OD content. OD addition impaired catalyst activities. However, in the presence of trace amounts of ethene, catalyst activities increased significantly even in the presence of high OD content.     

Copolymerization of ethylene/α‐olefins using bis(2‐phenylindenyl)zirconium dichloride metallocene catalyst: structural study of comonomer distribution

Catalysts have a major role in the polymerization of olefins and exert their influence in three ways: (1) polymerization behaviour, including polymerization activity and kinetics; (2) polymer particle morphology, including bulk density, particle size, particle size distribution and particle shape; and (3) polymer microstructure, including molecular weight regulation, chemical composition distribution and short‐ and long‐chain branching. By tailoring the catalyst structure, such as the creation of a bridge or introducing a substituent on the ligand, metallocene catalysts can play a major role in the achievement of desirable properties. Kinetic profiles of the metallocene catalyst used in this study showed decay‐type behaviour for copolymerization of ethylene/α‐olefins. It was observed that increasing the comonomer ratio in the feedstock affected physical properties such as reducing the melting temperature, crystallinity, density and molecular weight of the copolymers. It was also observed that the heterogeneity of the chemical composition distribution and the physical properties were enhanced as the comonomer molecular weight was increased. In particular, 2‐phenyl substitution on the indenyl ring reduced somewhat the melting point of the copolymers. In addition, the copolymer produced using bis(2‐phenylindenyl)zirconium dichloride (bis(2‐PhInd)ZrCl₂) catalyst exhibited a narrower distribution of lamellae (0.3–0.9 nm) than the polymer produced using bisindenylzirconium dichloride catalyst (0.5–3.6 nm). The results obtained indicate that the bis(2‐PhInd)ZrCl₂ catalyst showed a good comonomer incorporation ability. The heterogeneity of the chemical composition distribution and the physical properties were influenced by the type of comonomer and type of substituent in the catalyst. Copyright © 2010 Society of Chemical Industry     

Copolymerization of poly(1‐naphthylamine) with aniline and o‐toluidine

The commercial use of polyaniline has been impeded by its intractable nature and insolubility. The use of substituted polyaniline has been attempted mainly to increase the processibility of polyaniline, but this approach usually results in the lowering of the conductivity. This study reports the synthesis of poly(1‐naphthylamine), a fused ring derivative of polyaniline, and its copolymers with aniline and o‐toluidine via a chemical polymerization method. Spectral, thermal, morphological, and conductivity studies were carried out to elucidate the influence of the incorporation of aniline and o‐toluidine units into poly(1‐naphthylamine). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Copolymerization of ethylene/5‐ethylidene‐2‐norbornene with bis (2‐phenylindenyl) zirconium dichloride catalyst: I. Optimization of the operating conditions by response surface methodology

In this study, the copolymerization of ethylene with nonconjugated diene (5‐ethylidene‐2‐norbornene) was carried out with a bis(2‐PhInd) ZrCl₂ metallocene catalyst. Some polymerization factors that were considered affective on the catalyst activity, including comonomer content in the feed, ethylene pressure, and polymerization temperature, were investigated via response surface methodology to determine the optimum polymerization conditions. We found that the comonomer content in the feedstock had no enormous effect on the catalyst activity depression. Also, the polymerization temperature increment through the scrutinized range decreased the copolymerization activity. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Mechanistic in situ High‐Pressure NMR Studies of Benzene Hydrogenation by Supramolecular Cluster Catalysis with [(η6‐C6H6)(η6‐C6Me6)2Ru3(μ3‐O)(μ2‐OH)(μ2‐H)2][BF4]

In situ high‐pressure NMR spectroscopy of the hydrogenation of benzene to give cyclohexane, catalysed by the cluster cation [(η⁶‐C₆H₆) (η⁶‐C₆Me₆)₂Ru₃(μ₃‐O)(μ₂‐OH)(μ₂‐H)₂]⁺ 2 , supports a mechanism involving a supramolecular host‐guest complex of the substrate molecule in the hydrophobic pocket of the intact cluster molecule.     

Ethene/styrene-copolymerizations with [Me2C(3-RCp)(Flu)]ZrCl2/MAO (R=H,Me,tertBu,cHex, Ph)

Two new C₁-symmetric zirconocenes of the type [Me₂C(3-RCp)(Flu)]ZrCl₂ bearing a phenyl (Ph) or a cyclohexyl (cHex) substituent on the cyclopentadienyl ring were synthesized. Copolymerizations of ethene and styrene were carried out using these catalysts and compared to the results obtained with the methyl- and ^tertbutyl-substituted as well as with the unsubstituted system. By the introduction of the phenyl substituent both the activities and the molar masses could be increased whilst the styrene incorporation was comparable to that achieved with the unsubstituted system. In the case of the alkyl substituted systems (R=Me, ^tertBu, cHex) the styrene incorporation is decreased drastically and molar masses and activities are also strongly effected.     

Kinetic study on copolymerization of ethylene and 1‐hexene catalyzed by Cp2ZrCl2/MAO catalytic system

The kinetics of ethylene and 1‐hexene copolymerization catalyzed by Cp₂ZrCl₂/MAO was studied. A new kinetic mathematical model that takes the reactivation effect of MAO into account has been developed. Applying this model, the good agreement between the experimental data and the fitting profiles was achieved. POLYM. ENG. SCI., 47:540–544, 2007. © 2007 Society of Plastics Engineers     

3‐Naphthylindole Construction by Rhodium(II)‐Catalyzed Regioselective Direct Arylation of Indoles with 1‐Diazonaphthalen‐2‐(1H)‐ones

The regioselective direct 3‐arylation of indoles with 1‐diazonaphthalen‐2‐(1H)‐ones was developed by means of a rhodium(II) pivalate‐catalyzed cross‐coupling reaction. This procedure provided a variety of novel 3‐naphthylindoles in high yield. The direct coupling of benzofuran, pyrrole or furan with 1‐diazonaphthalen‐2‐(1H)‐ones afforded 2‐ or 3‐naphthyl substituted heterocycles.

     

Copolymerization of 2‐Acrylamido‐2‐methyl‐1‐propanesulfonic Acid and 1‐Vinylimidazole in Ethanol

Polymerization rate and copolymerization parameters of the free‐radical copolymerization of AMPS with 1‐VIm was studied as a function of the monomer feed and the pH value in ethanol. It was found that neutral and basic monomer mixtures containing the sodium salt of AMPS polymerized faster and led to polymers with a higher proportion of NaAMPS incorporated than those monomer mixtures containing the free acid. Additionally, based on the experimental data, copolymerization parameters of r_AMPS = 0.3 and r_1‐VIm = 0.13 were calculated for polymerization in acidic solution and r_AMPS = 4.1 and r_1‐VIm = 0.1 for polymerization in basic and neutral solutions. Finally, the thermal stability, rheological behavior, and intrinsic viscosity were determined for the polymers.

     

Preparation and properties of ethylene/POSS copolymer with rac‐Et(Ind)2ZrCl2 catalyst

The various monovinyl‐functional polyhedral oligomeric silsesquioxane (POSS) monomers had been copolymerized with ethylene (E) using rac‐Et(Ind)₂ZrCl₂ and a modified methylaluminoxane (MMAO) cocatalyst. The unreacted POSS monomer could be removed completely by washing the copolymerization product with n‐hexane. And the copolymers were characterized with ¹H NMR, TEM, DSC, TGA, and GPC to know the composition, thermal properties, molecular weight and its distribution, respectively. According to ¹H NMR data, the monomer reactivity ratios of various POSS monomers were calculated by the Fineman‐Ross and Kelen‐Tudos methods. Thermogravimetric analysis of E/POSS copolymers exhibited an improved thermal stability with a higher degradation temperature and char yields, demonstrating that the inclusion of inorganic POSS nanoparticles made the organic polymer matrix more thermally robust. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Hydrogenation of cis‐1,4‐poly(isoprene) catalyzed by OsHCl(CO)(O2)(PCy3)2

The quantitative hydrogenation of cis‐1,4‐poly(isoprene) (CPIP) provides an easy entry to the alternating copolymer of ethylene–propylene, which is difficult to prepare by conventional polymerization. The homogeneous hydrogenation of CPIP, in the presence of OsHCl(CO)(O₂)(PCy₃)₂ as catalyst, has been studied by monitoring the amount of hydrogen consumed during the reaction. The final degree of olefin conversion measured by computer‐controlled gas uptake apparatus was confirmed by infrared spectroscopy and ¹H nuclear magnetic resonance analysis. Kinetic experiments for CPIP hydrogenation in toluene solvent indicate that the hydrogenation rate is first order with respect to catalyst and carbon–carbon double bond concentration. A second‐order dependence on hydrogen concentration for low values and a zero‐order dependence for higher values of the hydrogen concentration was observed. The apparent activation energy for the hydrogenation of CPIP over the temperature range of 115–140°C was 109.3 kJ/mole. Mechanistic aspects of this catalytic process are discussed. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 142–152, 2003     

Copolymerization of n‐butylacrylate with styrene by a novel photoinitiator, 1‐(bromoacetyl)pyrene

A comparative study on photoinitiated solution copolymerization of n‐butylacrylate (BA) with styrene (Sty) using pyrene (Py), 1‐acetylpyrene (AP), and 1‐(bromoacetyl)pyrene (BP) as initiators showed that the introduction of a chromophoric moiety, bromoacetyl (? COCH₂Br), significantly increased the photoinitiating ability of pyrene. The kinetics and mechanism of copolymerization of BA with Sty using BP as photoinitiator have been studied in detail. The system follows nonideal kinetics (R_p ∝ [BP]^0.34 [BA]^1.07 [Sty]^0.97). The nonideality was attributed to both primary radical termination and degradative initiator transfer. The monomer reactivity ratios of Sty and BA have been estimated by the Finemann–Ross and Kelen–Tudos methods, by analyzing copolymer compositions determined by ¹H NMR spectra. The values of r₁ (Sty) and r₂ (BA) were found to be 0.78 and 0.25, respectively, which suggested the high concentration of alternating sequences in the random copolymers obtained. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3233–3239, 2006     

Ethylene/1‐octadecene copolymerization using [η5:η1‐C5Me4‐4‐R1‐6‐R‐C6H2O]TiCl2 catalysts

Copolymerization of ethylene with 1‐octadecene was studied using [η⁵:η¹‐C₅Me₄‐4‐R₁‐6‐R‐C₆H₂O]TiCl₂ [R₁ = ^tBu (1), H (2, 3, 4); R = ^tBu (1, 2), Me (3), Ph (4)] as catalysts in the presence of Al(i‐Bu)₃ and [Ph₃C][B(C₆F₅)₄]. The effect of the concentration of comonomer in the feed and Al/Ti molar ratio on the catalytic activity and molecular weight of the resultant copolymer were investigated. The substituents on the phenyl ring of the ligand affect considerably both the catalytic activity and comonomer incorporation. The 1 /Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system exhibits the highest catalytic activity and produces copolymers with the highest molecular weight, while the 2 /Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system gives copolymers with the highest comonomer incorporation under similar conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Copolymerization of ethylene with styrene using the catalyst system composed of Solvay-type TiCl3 and Cp2Ti(CH3)2

Summary Copolymerization of ethene and styrene was conducted at 40°C using the catalyst system composed of Solvay type TiCl₃ and Cp₂Ti(CH₃)₂. The crude polymer was fractionated with boiling chloroform to obtain 96.4 wt% of insoluble part, which was found to be a random copolymer of ethene and styrene. The copolymer was characterized in detail by DSC, ¹³C NMR, etc.