Polymerization with TMA-protected polar vinyl comonomers. I. Catalyzed by group 4 metal complexes with η5-type ligands

This paper describes the use of several kinds of group IV Cp based catalyst systems, in the synthesis of co- and terpolymers of ethylene, propylene and α-olefins endowed with OH and COOH functional groups. The hydroxy monomers used were 5-hexen-1-ol (4) and 10-undecen-1-ol (5) and the carboxy monomer was 10-undecen-1-oic acid (6). The three catalyst systems used were the C₂ symmetric ansa-zirconocene (1) the “in-site” titanium complex (2) and the non-rigid zirconocene (3), all activated by methylaluminoxane. Trimethylaluminium was used to protect the functional group of polar monomers. The first two catalyst systems suffer similar activity loss in the presence of polar monomer whereas the third one exhibited better tolerance toward the hydroxyolefins. NMR and FTIR spectroscopies were used to characterize the polymerization products. All three catalyst systems afforded functionalized co- and terpolymers by direct polymerization of ethylene/propylene/hydroxy-α-olefins but only the catalyst system (1)/MAO displays appreciable activities for direct polymerization of ethylene, propylene and carboxy-α-olefins. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2457–2469, 1999     

Polymerizations of olefins and diolefins catalyzed by monocyclopentadienyltitanium complexes containing a (dimethylamino)ethyl substituent and comparison with ansa-zirconocene systems

{[2-(dimethylamino)ethyl]cyclopentadienyl}titanium trichloride (Cp^NTiCl₃, 1 ) was activated with methylaluminoxane (MAO) to catalyze polymerizations of ethylene (E), propylene (P), ethylidene norbornene (ENB), vinylcyclohexene (VCH), and 1,4-hexadiene (HD). The dependence of homopolymerization activity ( A ) of 1 /MAO on olefin concentration ([M]ⁿ) is n = 2.0 ± 0.5 for E and n = 1.8 ± 0.2 for P. The value of n is 2.4 ± 0.2 for CpTiCl₃/MAO catalysis of ethylene polymerization; this system does not polymerize propylene. 1 /MAO catalyzes HD polymerization at one-tenth of A _H for 1-hexene, probably because of chelation effects in the HD case. The copolymerization of E and P has reactivity ratios of r_E = 6.4 and r_P = 0.29 at 20°C, and r_Er_P = 1.9, which suggests 1 /MAO may be a multisite catalyst. The copolymerization activity of CpTiCl₃/MAO is 50 times smaller than that of Cp^NTiCl₃/MAO. Terpolymerization of E/P/ENB has A of 10⁵ g of polymer/(mol of Ti h), incorporates up to 14 mol % (∼ 40 wt %) of ENB, and high MW's of 1 to 3 × 10⁵. All of these parameters are surprisingly insensitive to the ENB concentration. The E/P/VCH terpolymerization has comparable A value of (1.3 ± 0.3) × 10⁵ g/(mol of Ti h). The incorporation of VCH in terpolymer increases with increasing [VCH]. Terpolymerization with HD occurs at about one-third of the A of either ENB or VCH; the product HD–EPDM is low in molecular weight and contains less than 4% of HD. These terpolymerization results are compared with those obtained previously for three zirconocene precursors: rac-ethylenebis(1-η⁵-indenyl)dichlorozirconium ( 6 ), rac-(dimethylsilylene)bis(1-η⁵-indenyl)dichlorozirconium ( 7 ), and ethylenebis(9-η⁵-fluorenyl)dichlorozirconium ( 8 ). The last compound is a particularly poor terpolymerization catalyst; it incorporates very little VCH or HD and no ENB at all. 7 /MAO is a better catalyst for E/P/VCH terpolymerization, while 6 /MAO is superior in E/P/HD terpolymerization. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 319–328, 1998     

Functionalization of polyethylene based on metallocene catalysis and its application to syntheses of new graft copolymers possessing polar polymer segments

The control of hydroxylated polyethylene (PE) structures was investigated in the copolymerization of ethylene with allyl alcohol or 10-undecen-1-ol with a specific metallocene, methylaluminoxane, and trialkyl aluminum catalyst system through changes in the copolymerization conditions. The incorporation of allyl alcohol into the PE backbones was controllable through changes in the trialkyl aluminum, leading to terminally hydroxylated PE or a copolymer possessing hydroxyalkyl side chains. The copolymerization of ethylene with 10-undecen-1-ol gave copolymers with hydroxyalkyl side chains of various contents with a variety of molecular weights through changes in the copolymerization conditions. The obtained copolymers were useful as macroinitiators that allowed polar polymer segments to grow on the PE backbones, leading to the creation of graft copolymers that possessed PE and polar polymer segments. In this way, polyethylene-g-poly(propylene glycol) (PE-g-PPG) and polyethylene-g-poly(ϵ-caprolactone) (PE-g-PCL) were synthesized. The ¹³C NMR analysis of PE-g-PPG suggested that all the hydroxyl groups were consumed for propylene oxide polymerization, and transmission electron microscopy demonstrated nanoorder phase separation and indistinct phase boundaries. ¹³C NMR and gel permeation chromatography analyses indicated the formation of PE-g-PCL, in which 36–80 mol % of the hydroxyl groups worked as initiators for ϵ-caprolactone polymerization. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3657–3666, 2003     

Compatibilization of polyethylene/polyamide 6 blends with functionalized polyethylenes prepared with metallocene catalyst

Metallocene catalyst technology was utilized to prepare functionalized polyethylenes, which were used as compatibilizers in polyethylene/polyamide 6 (40/60) blends. Polymerization of ethylene with 10-undecen-1-ol, 10-undecenoic acid, or N-methyl-10-undecenylamine resulted in ethylene copolymers with a small amount (0.2–1.2 mol %) of functionalized side chains. The blends were prepared in a twin-screw midiextruder, and injection molded with a mini-injection molding machine. The effect of the new compatibilizers on morphology and mechanical and thermal properties was studied. Toughness as well as stiffness and strength increased significantly with an addition of 10 wt % compatibilizer. Morphology became much more uniform, and crystallization and melting behavior changed. The Molau test with FTIR analysis was used to determine that the desired reactions between the compatibilizer and polyamide had actually taken place. The results showed functionalized polyethylenes prepared with metallocene catalysts to act as effective compatibilizers in polyethylene/polyamide 6 blends. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3099–3108, 1999     

Highly active methyl methacrylate polymerization catalysts obtained from bis(3,5‐dinitro‐salicylaldiminate)nickel(II) complexes and methylaluminoxane

The homopolymerization of methyl methacrylate was investigated with bis(salicylaldiminate)nickel(II) complexes, such as bis[3,5‐dinitro‐N(2,6‐diisopropylphenyl)salicylaldiminate]nickel(II) ( IIIa ) and bis[3,5‐dinitro‐N(phenyl)salicylaldiminate]nickel(II) ( IIIb ), and with methylaluminoxane (MAO) as an activator. In particular, the effect of the Al/Ni molar ratio on the catalytic activity and on the properties of the resulting poly(methyl methacrylate) (PMMA) was checked. The maximum activity was ascertained when an Al/Ni molar ratio equal to about 100 was used. However, the productivity of the catalytic systems was rather low. When the IIIa /MAO catalytic system was prepared under an ethylene atmosphere, an extremely high activity was observed, a productivity value of up to around 150,000 g of PMMA/(mol of Ni × h) being obtained, the highest ever found with nickel‐based catalysts. No appreciable presence of ethylene counits in the polymeric products was also ascertained. When the IIIb /MAO system was used, similar results were found, and high molecular weight PMMAs were obtained, despite the absence of bulky isopropyl substituents in positions ortho and ortho′ to the N‐aryl moiety of the salicylaldiminate ligand. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2117–2124, 2003     

Ethylene polymerization with FI complexes having novel phenoxy‐imine ligands: Effect of metal type and complex immobilization

A series of bis(phenoxy‐imine) vanadium and zirconium complexes with different types of R³ substituents at the nitrogen atom, where R³ = phenyl, naphthyl, or anthryl, was synthesized and investigated in ethylene polymerization. Moreover, the catalytic performance was verified for three supported catalysts, which had been obtained by immobilization of bis[N‐(salicylidene)‐1‐naphthylaminato]M(IV) dichloride complexes (M = V, Zr, or Ti) on the magnesium carrier MgCl₂(THF)₂/Et₂AlCl. Catalytic performance of both supported and homogeneous catalysts was verified in conjunction with methylaluminoxane (MAO) or with alkylaluminium compounds (Et_nAlCl_3?n, n = 1–3). The activity of FI vanadium and zirconium complexes was observed to decline for the growing size of R³, whereas the average molecular weight (MW) of the polymers was growing for larger substituent. Moreover, vanadium complexes exhibited the highest activity with EtAlCl₂, whereas zirconium ones showed the best activity with MAO. All immobilized systems were most active in conjunction with MAO, and their activities were higher than those for their homogeneous counterparts, and they gave polymers with higher average MWs. That effect was in particular evident for the titanium catalyst. The vanadium complex 3 was also a good precursor for ethylene/1‐octene copolymerization; however, its immobilization reduced its potential for incorporation of a comonomer into a polyethylene chain. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

N‐(2‐benzimidazolylquinolin‐8‐yl)benzamidate half‐titanocene chlorides: Synthesis,characterization and their catalytic behavior toward ethylene polymerization

A series of N‐(2‐benzimidazolyquinolin‐8‐yl)benzamidate half‐titanocene chlorides, Cp′TiLCl ( C1 – C8 : Cp′ = C₅H₅, MeC₅H₄, or C₅Me₅; L = N‐(benzimidazolyquinolin‐8‐yl)benzamides)), was synthesized by the KCl elimination reaction of half‐titanocene trichlorides with the correspondent potassium N‐(2‐benzimidazolyquinolin‐8‐yl)benzamide. These half‐titanocene complexes were fully characterized by elemental and NMR analyses, and the molecular structures of complexes C2 and C8 were determined by the single‐crystal X‐ray diffraction. The high stability of the pentamethylcyclopentadienyl complex ( C8 ) was evident by no decomposing nature of its solution in air for one week. The oxo‐bridged dimeric complex ( C9 ) was isolated from the solution of the corresponding cyclopentadienyl complex ( C3 ) solution in air. Complexes C1 – C8 exhibited good to high catalytic activities toward ethylene polymerization and ethylene/α‐olefin copolymerization in the presence of methylaluminoxane (MAO) cocatalyst. In the typical catalytic system of C1/ MAO, the polymerization productivities were enhanced with either elevating reaction temperature or increasing the ratio of MAO to titanium precursor. In general, it was observed that higher the catalytic activity of the catalytic system lower the molecular weight of polyethylene. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3154–3169, 2009     

Copolymerization of ethylene/unsaturated alcohols using nickel catalysts: effect of the ligand on the activity and comonomer incorporation

The nickel complexes {bis[N,N′-di(2-t-butylphenyl)imino]acenaphthene} dibromonickel (1-NiBr₂) and {bis[N,N′-di(2-phenylphenyl)imino]acenaphthene} dibromonickel (2-NiBr₂) were studied in homo-, co- and terpolymerization of ethylene and propylene with polar monomers and the results compared to those previously obtained with another catalyst precursor [bis(N,N′-dimesitylimino)acenaphthene] dibromonickel (3-NiBr₂). In order to understand the effect of the ligand in the activity and rate of comonomer incorporation some theoretical studies, using both a semi-empirical molecular orbital method and a density-functional theory model, were performed. Good agreement was found between the computed parameters and the experimental results for the order of homo-polymerization, the differences in polymer molecular weight distribution, and, in some cases, the incorporation of functionalized copolymers in the case of copolymerization, and also on the inhibition effects caused by these copolymers.     

Highly active and easily accessible catalysts for vinyl polymerization of norbornene obtained by oxidative addition of salicylaldimine ligands to bis(1,5‐cyclooctadiene)nickel(0) and methylaluminoxane

Highly active, cheap, and easy to synthesize catalytic systems, obtained in situ by the oxidative addition of salicylaldimine ligands to bis(1,5‐cyclooctadiene)nickel(0) and activated by methylaluminoxane (MAO), are now reported for the vinyl polymerization of norbornene. Their activity resulted mainly influenced by the nature of the substituents present both on the phenolate moiety and on the N‐aryl ring as well as the content of free trimethylaluminum (TMA) present in the commercial MAO. In particular, the maximum activity, up to about 78,000 kg polynorbornene/mol Ni × h, was ascertained when 3,5‐dinitro‐N‐(2,6‐diisopropylphenyl)salicylaldimine ligand was adopted in conjunction with Ni(cod)₂ and TMA‐depleted MAO. This remarkable performance, to the best of our knowledge, the highest never reported working in toluene instead of chlorinated aromatics, was reached adopting this more sustainable reaction medium. The influence of the main reaction parameters such as reaction time, temperature, monomer/Ni, and Al/Ni molar ratios on the catalytic performances and polymer characteristics was studied as well. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Synthesis and characterization of poly(aryl amide imide)s derived from diphenyltrimellitic anhydride

The synthesis and characterization of a series of novel poly(aryl amide imide)s based on diphenyltrimellitic anhydride are described. The poly(aryl amide imide)s, having inherent viscosities of 0.39–1.43 dL/g in N-methyl-2-pyrrolidinone at 30°C, were prepared by polymerization with aromatic diamines in N,N-dimethylacetamide and subsequent chemical imidization. All the polymers were amorphous, readily soluble in aprotic polar solvents such as DMAC, NMP, dimethylsulfoxide, N,N-dimethylformamide, and m-cresol, and could be cast to form flexible and tough films. The glass transition temperatures were in the range of 284–366°C, and the temperatures for 5% weight loss in nitrogen were above 468°C. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4541–4545, 1999     

Synthesis of regiocontrolled polymer having 2-naphthol unit by CuCl-amine catalyzed oxidative coupling polymerization

Regiocontrolled polymer (2) having 2-naphthol unit was prepared by oxidative coupling polymerization of bis(2-naphthol) (1). Polymerizations were conducted in dichloromethane in the presence of [di-μ-hydroxo-bis(N,N,N′,N′-tetramethylethylenediamine)copper(II)] chloride [CuCl(OH)TMEDA] under air at room temperature, producing polymers with number-average molecular weights up to 12,000. The structure of polymer 2 was characterized by 270 MHz ¹H–NMR and 68.5 MHz ¹³C–NMR spectroscopies and was estimated to consist almost completely of 1,1′-linkage. The polymer was readily soluble in polar aprotic solvents and tetrahydrofuran at room temperature. Thermogravimetric analysis of polymer 2 showed 10% weight loss at 450°C in nitrogen. The model reactions were studied to clarify the applicability of CuCl(OH)TMEDA for coupling of naphthol derivatives. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3702–3709, 1999     

SYNTHESIS,CHARACTERIZATION AND ELECTROCHEMICAL STUDIES OF MONO- AND DINUCLEAR COMPLEXES OF NICKEL(II) AND COBALT(II) WITH HEXADENTATE LIGANDS HAVING N2P4 DONOR ATOMS. CRYSTAL STRUCTURE OF [Ni(BDPE)]ClO4)2. CH2Cl2

Abstract

A series of mono- and dinuclear complexes of Ni(II) and Co(II) with two hexadentate ligands α,α′-bis(bis(2-(diphenylphosphino)ethyl)amino)ethane(BDPE) and α,α′-bis(bis(2-(diphenylphosphino)ethyl)-amino)-m-xylene (BDPX) were synthesized and chracterized by means of elemental analyses, molar conductance, magnetic susceptibilities, infrared, electronic and ³¹P NMR data. The molecular structure of a mononuclear Ni(II) complex, [Ni(BDPE)](CIO₄)₂.CH₂Cl₂, was established by single-crystal X-ray diffraction methods. Crystal data: C₅₉H₆₂NiCl₄N₂O₈P₄, M = 1250.98, orthorhombic, space group Pbca, V= 11834.3(7) Å3, Z= 8, a= 10.817(1), b = 31.683(7), c=34.538(1) Å, final R 0.055 (R w = 0.057) for 3118 observed reflections. The Ni(II) ion exists in a slightly distorted square planar geometry, the coordination sites being two phosphorous and two tertiary nitrogen atoms of the ligand. Electrochemical studies of the complexes were also carried out.     

Synthesis and characterization of novel poly(amide-imide)s containing hexafluoroisopropylidene linkage

A series of novel soluble poly(amide-imide)s were prepared from the diimide-dicarboxylic acid, 2,2-bis[N-(4-carboxyphenyl)-phthalimidyl]hexafluoropropane, with various diamines by the direct polycondensation in N-methyl-2-pyrrolidinone containing CaCl₂ using triphenyl phosphite and pyridine as condensing agents. All the polymers were obtained in quantitative yields with inherent viscosities of 0.78–1.63 dL g⁻¹. The polymers were amorphous and readily soluble in aprotic polar solvents such as N-methyl-2-pyrrolidinone, N,N-dimethylacetamide, N,N-dimethylformamide, and dimethyl sulfoxide as well as in less polar solvents such as pyridine and γ-butyrolactone, and also in tetrahydrofuran. The polymer films had tensile strength of 84–129 MPa, an elongation at break range of 6–22%, and a tensile modulus range of 2.0–2.7 GPa. The glass transition temperatures of the polymers were determined by DSC method and they were in the range of 240–282°C. These polymers were fairly stable up to a temperature around or above 400°C, and lose 10% weight in the range of 450–514°C and 440–506°C in nitrogen and air, respectively. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2629–2635, 1999     

Well-defined vanadium complexes as the catalysts for olefin polymerization

The design and synthesis of well-defined vanadium complexes as efficient catalysts for olefin polymerization remains an attractive project for organometallic and polymeric research. Recently, vanadium complexes with well-defined structures have been explored for olefin (co)polymerization by several groups around the world. This article summarizes our recent progress in well-defined vanadium complexes bearing a variety of chelating β-enaminoketonato, salicylaldiminato, iminopyrrolide and tetradentate amine trihydroxy ligands, and their applications in ethylene polymerization, ethylene/α-olefin copolymerization and ethylene/cycloolefin copolymerization. The application of the optimized catalysts in the copolymerization of ethylene and polar monomer such as 3-buten-1-ol, 5-hexen-1-ol, 10-undecen-1-ol and 5-norbornene-2-methanol is also discussed. Particular attention has been paid to the relationships between the catalytic behavior and the electronic and geometrical structure of the precatalyst.     

Synthesis and ethylene polymerization of 8‐(fluorenylarylimino)‐5,6,7‐trihydroquinolylnickel chlorides: Tailoring polyethylenes by adjusting fluorenyl position and adduct Et2Zn

A series of 8‐(arylimino)‐5,6,7‐trihydroquinolines ligand pendant fluorenyl group at N‐aryl ring, and their nickel complexes ( Ni1 ? Ni5 ) have been prepared and characterized. Once activated with Et₂AlCl, the complexes Ni1 , Ni2 , and Ni3 bearing ligands from para‐fluorenylaniline produced unimodal polyethylenes; on the contrary complexes Ni4 and Ni5 gave bimodal polyethylenes due to steric influence of ligands from ortho‐fluorenyl anilines. With a increment of Et₂Zn/ Ni4 ratio from 0 to 400, the distinct bimodel polyethylenes were obtained with molecular weights shifted from 14.3 to 57.6 kg·mol^?1; apart shiftment to higher molecular weights, the portion of low molecular weight decreased along with higher portion of high molecular weight. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1910–1919     

Synthesis and characterization of new soluble polyamides derived from 3,3′,5,5′-tetramethyl-2,2-bis[4-(4-carboxyphenoxy)phenyl]propane

A series of new soluble polyamides having isopropylidene and methyl-substituted arylene ether moieties in the polymer chain were prepared by the direct polycondensation of 3,3′,5,5′-tetramethyl-2,2-bis[4-(4-carboxyphenoxy)phenyl]propane and various diamines in N-methyl-2-pyrrolidinone (NMP) containing CaCl₂ using triphenyl phosphite and pyridine as condensing agents. Polymers were produced with moderate to high inherent viscosities of 0.85–1.47 dL g⁻¹ while the weight-average molecular weight and number-average molecular weight were in the range of 86,700–259,000 and 43,300–119,000, respectively. All the polymers were readily dissolved in polar aprotic solvents such as NMP, N,N-dimethylacetamide, and N,N-dimethylformamide, as well as less polar solvents such as m-cresol and pyridine, and even soluble in tetrahydrofuran. These polymers were solution-cast into transparent, flexible and tough films. All of the polymers were amorphous and the polyamide films had a tensile strength range of 82–122 MPa, an elongation at break range of 6–18%, and a tensile modulus range of 2.0–2.8 GPa. These polyamides had glass transition temperatures between 233–260°C and 10% weight loss temperatures in the range of 450–489 and 459–493°C in nitrogen and air atmosphere, respectively. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1997–2003, 1999     

Polyelectrolyte complexes. II. Specific aspects of the formation of polycation/dye/polyanion complexes

We report on the formation of the polycation/dye/polyanion (PC/D/PA) complexes by the interaction between nonstoichiometric polycation/dye (PC/D) complexes with polyanions. Polycations differed in their content of the (N,N‐dimethyl‐2‐hydroxypropylene ammonium chloride) units in the main chain. Poly(sodium acrylate) (NaPA), poly(sodium 2‐acrylamido‐2‐methylpropane sulfonate) (NaPAMPS) and poly(sodium styrenesulfonate) (NaPSS) were used as polyanions. Crystal Ponceau 6R (CP6R) and Ponceau 4R (P4R) with two or three sulfonic groups were used as anionic dyes. The interaction between nonstoichiometric PC/D complexes and polyanions was followed by UV‐VIS spectroscopy, viscometry, and conductometry measurements. Formation of PC/D/PA complexes takes place mainly by the electrostatic interaction between the polyanion and the free positive charges of the nonstoichiometric PC/D complex. The stoichiometry and the stability of the tricomponent complexes depended on the polycation structure, the structure and molecular weight of polyanion, the dye structure, and the P/D molar ratio. A high amount of the dye was excluded from the complex before the end point when a branched polycation was used. The higher the solubility of the dye the lower the stability of the PC/D/PA complexes. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 409–418, 1999     

Alkylaluminum activator effects on polyethylene branching using a N,N′‐nickel precatalyst appended with bulky 4,4′‐dimethoxybenzhydryl groups

Ten unsymmetrical N,N'‐bis (imino) acenaphthene‐nickel (II) halide complexes, [1‐[2,6‐{(4‐MeOC₆H₄)₂CH}₂–4‐MeC₆H₂N]‐2‐(ArN)C₂C₁₀H₆]NiX₂, each appended with one N‐2,6‐bis(4,4'‐dimethoxybenzhydryl)‐4‐methylphenyl group, have been synthesized and characterized. The molecular structures of Ni1 , Ni3 , Ni5 and Ni6 highlight the variation in steric protection afforded by the inequivalent N‐aryl groups; a distorted tetrahedral geometry is conferred about each nickel center. On activation with diethylaluminum chloride (Et₂AlCl) or methylaluminoxane (MAO), all complexes showed high activity at 30°C for the polymerization of ethylene with the least bulky bromide precatalysts ( Ni1 and Ni4 ), generally the most productive, forming polyethylenes with narrow dispersities [M_w/M_n: < 3.4 (Et₂AlCl), < 4.1 (MAO)] and various levels of branching. Significantly, this level of branching can be influenced by the type of co‐catalyst employed, with Et₂AlCl having a predilection towards polymers displaying significantly higher branching contents than with MAO [T_m: 33.0–82.5°C (Et₂AlCl) vs. 117.9–119.4°C (MAO)]. On the other hand, the molecular weights of the materials obtained with each co‐catalyst were high and, in some cases, entering the ultra‐high molecular weight range [M_w range: 6.8–12.2 × 10⁵ g mol^?1 (Et₂AlCl), 7.2–10.9 × 10⁵ g mol^?1 (MAO)]. Furthermore, good tensile strength (ε_b up to 553.5%) and elastic recovery (up to 84%) have been displayed by selected more branched polymers highlighting their elastomeric properties.     

Copolymerization of styrene and butadiene with Ni(acac)2-methylaluminoxane catalyst

Copolymerization of styrene (St) and butadiene (Bd) with nickel(II) acetylacetonate [Ni(acac)₂]-methylaluminoxane (MAO) catalyst was investigated. Among the metal acetylacetonates [Mt(acac)_x] examined, Ni(acac)₂ showed a high activity for the copolymerization of St and Bd giving copolymers having high cis-1,4-microstructure in Bd units in the copolymer. The effect of alkylaluminum as a cocatalyst on the copolymerization of St and Bd with the Ni(acac)₂-MAO catalyst was observed, and MAO was found to be the most effective cocatalyst for the copolymerization. The monomer reactivity ratios for the copolymerization of St and Bd with the Ni(acac)₂-MAO catalyst were determined to be r_St = 0.07 and r_Bd = 3.6. Based on the obtained results, it was presumed that the random copolymers with high cis-1,4-microstructure in Bd units could be synthesized with the Ni(acac)₂-MAO catalyst without formation of each homopolymer. The polymerization mechanism with the Ni(acac)₂-MAO catalyst was also discussed. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3838–3844, 1999     

Synthesis and Mechanical Properties of Polypropylene-based Polymer Hybrids via Controlled Radical Polymerization

Isotactic polypropylene-based graft copolymers linking poly(methyl methacrylate), poly(n-butyl acrylate) and polystyrene were successfully synthesized by a controlled radical polymerization with isotactic polypropylene (iPP) macroinitiator. The hydroxylated iPP, prepared by propylene/10-undecen-1-ol copolymerization with a metallocene/methyl-aluminoxane/triisobutylaluminum catalyst system, was treated with 2-bromoisobutyryl bromide to produce a Br-group containing iPP (PP-g-Br). The resulting PP-g-Br could initiate controlled radical polymerization of methyl methacrylate, n-butyl acrylate and styrene by using a copper catalyst system, leading to a variety of iPP-based graft copolymers with a different content of the corresponding polar segment. These graft copolymers demonstrated unique mechanical properties dependent upon the kind and content of the grafted polar segment.