Higher Comonomer Incorporation Research Articles

Designing easily accessible tridentate hafnium catalysts for ethylene/1-octene copolymerization

Polyolefin elastomers (POEs) have attracted widespread interest in both academia and industry as an important class of polyolefin material. Catalyst plays a critical role in the production of high-performance POEs. In this study, we design and synthesize a series of easily accessible tridentate pyridine amino hafnium catalysts with flexible ligands and study their properties in ethylene polymerization and copolymerization with 1-octene. These tridentate pyridine amino hafnium catalysts exhibited activity of up to 3.1 × 106 g mol−1 h−1, producing polyethylene with high molecular weight of up to 64.8 × 104 g mol−1 in ethylene polymerization at 150 °C. More importantly, these hafnium catalysts produced ethylene/1-octene copolymers with high comonomer incorporation of up to 12.9 mol% and molecular weight of up to 111.9 × 104 g mol−1(Mw), along with great mechanical properties (stress up to 17 MPa and strain up to 1000 %).

Efficient copolymerization of ethylene with norbornene mediated by phosphine-sulfonate palladium catalysts

A series of tBu-/Ar-substituted phosphine-sulfonate palladium catalysts Pd1-Pd6 {[κ2(P, O)-(tBu)ArP(C6H4SO2O)]Pd(Me)(DMSO)} (1: Ar = Ph; 2: Ar = 4-OMe-C6H4; 3: Ar = 4-CF3-C6H4; 4: Ar = 2-OMe-C6H4; 5: Ar = 2,5- (OMe)2-C6H3; 6: Ar = 2,4-(OMe)2-C6H3) were prepared to copolymerize ethylene with norbornene and its polar derivatives. Installing electron-donating OMe substituent on the nonchelating P-bound aryl was proven to enhance the properties of catalysts. The position and number of OMe substituent significantly influenced the copolymerization results. The E-NB copolymers generated from these catalysts showed both high comonomer incorporations (≥19.3 mol%) and high copolymer molecular weights (≥24.6 kg⋅mol−1), which has been proven to be difficult to achieve using this catalyst system. And for the obtained copolymers, their norbornene incorporations and Tg values conformed to a linear relationship. More importantly, these catalysts can efficiently mediate the copolymerizations of ethylene and polar norbornenes, along with high activities (up to 1.0 × 106 g⋅mol−1⋅h−1), high molecular weights (up to 182 kg⋅mol−1), and high incorporations (up to 36.7 mol%). This work provided an efficient method to synthesis cyclic olefin copolymer using late transition metal catalysts.

Significant cooperative effects in binuclear titanium complexes based on trifluoromethyl substituted bis-β-carbonylenamine ligands for ethylene (co)polymerization

The binuclear cooperative effect could greatly improve the catalytic performances for olefin polymerization but has rarely been utilized in early transition nonmetallocene binuclear complexes. Here a series of m- and p-phenylene-bridged bis-β-carbonylenamine ligands and the corresponding binuclear titanium complexes (Ti2mLa-Ti2mLc, Ti2pLa) were synthesized and characterized, with the molecular structure of ligand mLa further characterized by single crystal X-ray diffraction, which indicated that methylthio aniline reacted with the carbonyl next to trifluoromethyl group, thus led to relatively short metal-metal separation in binuclear complexes. Activated by MAO, the binuclear complex Ti2mLa exhibited the highest activity for ethylene polymerization and ethylene/α-olefins copolymerization, and the highest comonomer incorporation, relative to other binuclear Ti2mLb, Ti2mLc and Ti2pLa and mononuclear Ti1La. For ethylene polymerization, the activity of complex Ti2mLa was almost 4 and 2.6 times those of p-phenylene-bridged derivative Ti2pLa and mononuclear Ti1La, and the activity of complex Ti2mLa for ethylene/1-hexene copolymerization was 2 and 4.8 times those of Ti2pLa and Ti1La. Furthermore, the incorporation of comonomer for ethylene/1-hexene copolymerization produced by Ti2mLa was more than twice that of Ti2pLa and triple that of Ti1La. All these results clearly showed that stronger bimetallic cooperative effect existed in binuclear titanium complex Ti2mLa due to shorter metal-metal distance.

Synthesis of Si‐O‐Si bridged diamido Group 4 complexes and the applications to polymerization of olefins

Titanium, zirconium, and hafnium complexes O[Me2Si(Dip)N]2MCl2 [Dip = 2,6‐iPr2C6H3; M = Ti (1), Zr (2), Hf (3)], O[Me2Si(tBu)N]2ZrCl2 (4), and O[iPr2Si(Dip)N]2ZrCl2 (5) supported by Si‐O‐Si bridged diamido ligands were synthesized. X‐ray diffraction analysis disclosed that complex 2 displays a distorted trigonal bipyramidal geometry. Complexes 1–5, upon the activation with sMAO, exhibited diverse catalytic performance for the polymerization of ethylene and copolymerization of ethylene with norbornene or 1‐octene. For ethylene homopolymerization, both complexes 1–2 are good catalysts giving polymer with high molecular weight and narrow polydispersities. Complex 2 catalyzed copolymerization of ethylene with 1‐octene exhibiting high catalytic activity but with norbornene showing moderate activity, affording corresponding high molecular weight copolymers with relatively high comonomer incorporations of 11% and 29%, respectively.

Zirconium Complexes with Bulkier Amine Bis(phenolate) Ligands and Their Catalytic Properties for Ethylene (Co)polymerization.

A series of new zirconium complexes bearing bulkier amine bis(phenolate) tetradentate ligands, Me2NCH2CH2N{CH2(2-O-3-R-5-tBu-C6H2)}2ZrCl2 [R = CPhMe2 (1); CMePh2 (2); CPh3 (3); Ph (4); 3,5-Me2C6H3 (5); 3,5-tBu2C6H3 (6); 4-tBuC6H4 (7)], were synthesized and characterized by 1H nuclear magnetic resonance (NMR), 13C NMR, and elemental analyses. The molecular structures of complexes 1 and 3 were determined by single-crystal X-ray diffraction analysis. The X-ray crystallography analysis reveals that these complexes display a slightly distorted octahedral geometry around their metal centers. Upon activation with methylaluminoxane (MAO), dry-MAO, MAO/butylated hydroxytoluene (BHT), or AliBu3/CPh3B(C6F5)4, these zirconium complexes exhibit high catalytic activity for ethylene polymerization [up to 1.07 × 107 g PE (mol Zr)-1 h-1] and ethylene/1-hexene copolymerization [up to 2.78 × 107 g polymer (mol Zr)-1 h-1], affording (co)polymers with moderate to high molecular weights and good comonomer incorporations. The zirconium complexes with bulkier R groups show higher catalytic activities and longer lifetimes and produce polymers with higher molecular weights, while the zirconium complexes with aryls as R groups demonstrate relatively good comonomer incorporation ability for the copolymerization reactions. These catalytic systems also show moderate catalytic activities for the polymerization reactions of propylene, 1-hexene, and 1-decene. Upon activation with MAO, the zirconium complexes also show moderate catalytic activities for the copolymerization reaction of ethylene with 3-buten-1-ol (treated with 1 equiv of AliBu3), affording copolymers with the incorporation of 3-buten-1-ol up to 1.05%.

Functionalized amphiphilic polyethylene via direct copolymerizations of ethylene with α-olefin containing amino functionalization

Transition metal-catalyzed copolymerization of olefins with polar monomers signifies a challenge because transition metal catalysts usually easily get poisoned by heteroatoms. Novel amino-containing polyethylene with high molecular weight, fluorescent functionality was synthesized by direct copolymerization of ethylene and amino-olefin containing shielding groups. The highly efficient non-metallocene catalyst system with high tolerance to polar monomers [N, P] complexes [silicon bridged diphenyl phosphorus-phenyl-amine multi chelated] can effectively promote the copolymerization of ethylene and amino-olefins containing considerable group protection, in which the catalysts very high catalytic activity (up to 6.56 × 104 g mol−1 h−1) was achieved. The functional copolymer exhibited high molecular weight (up to 2.87 × 105 g mol–1) and amino-olefin comonomer incorporation (up to 2.43 mol%). Remarkably, the copolymer showed a high melting point (T m around 138.7 °C) and thermal stability. The incorporated amino acid ester unit changes the surface characteristics of the polyolefin, making it have excellent hydrophilicity and fluorescence. Furthermore, as the content of functional copolymer increases, the properties both have significantly increased.

The Stronger the Better: Donor Substituents Push Catalytic Activity of Molecular Chromium Olefin Polymerization Catalysts.

The donor strength of bifunctional pyridine‐cyclopentadienyl ligands was altered systematically by the introduction of donating groups in the para‐position of the pyridine. In the resulting chromium complexes an almost linear correlation between donor strength and the nitrogen‐chromium distance as well as the electronic absorption maximum is experimentally observed. The connection of electron‐donating groups in the ligand backbone leads to an efficient transfer of the electronic influences to the catalytically active metal centre without restricting it through steric effects. Therefore, catalytic olefin polymerization activity, which is already very high for the previously studied catalysts, increase considerably by attaching para‐amino groups to the chelating pyridine or quinoline, respectively. Combining electron‐rich indenyl ligands with para‐amino substituted pyridines lead to the highest catalytic activities observed so far for this class of organo chromium olefin polymerisation catalysts. The resulting polymers are of ultra‐high molecular weight and the ability of the catalysts to incorporate co‐monomers is also very high.

Progress in vanadium complex catalysts and their catalytic behavior toward copolymerization of ethylene with α-olefins

<p indent=0mm>Ethylene-propylene rubber, linear low density polyethylene and polyolefin elastomer, which are prepared by copolymerization of ethylene with α-olefins, have an important market share of the industry due to their excellent properties. Catalyst plays important roles in the copolymerization of ethylene with α-olefins. Many vanadium complexes in the oxidation states of +3, +4 and +5 have been developed as precatalyst for the copolymerization. The progress of vanadium complex catalysts and their use in copolymerization of ethylene with α-olefins were reviewed. The effects of chelated ligands on the catalytic activity of catalysts, composition, molecular weight, molecular weight distribution and sequence of the resulting copolymers were discussed. Vanadium(III) complexes are widely used since vanadium(III) species are usually considered as active species in olefin coordination polymerization. Vanadium(III) complexes bearing monodentate <italic>N</italic>-heterocyclic carbene (NHC) ligand or bidentate β-diketonate ligands have been used as prcatalyst in copolymerization of ethylene with propylene, affording ethylene-propylene copolymers with high propylene content. Ethylene-propylene copolymers with ultra-high molecular weight were prepared by using vanadium(III) complexes containing NHC ligand. Vanadium(III) complexes bearing chelated bidentate N^N or N^O, etc. ligands show high catalytic activity up to <sc>8820 kg mol^–1 h^–1</sc> toward copolymerization of ethylene with 1-hexene. The introduction of bulky substitutes on the ligand results in an increase in the reactive ratio of ethylene and a decrease in the reactive ratio of 1-hexene, and thus a change in the sequence of monomer in the resulting copolymer. Vanadium(III) complexes containing tridentate and tetradentate ligands display relatively lower catalytic activity than their analogues containing similar bidentate ligand. Most vanadium(IV) complexes display lower catalytic activity than vanadium(III) complexes bearing similar ligands. Ethylene-propylene copolymer with high propylene content could be prepared by copolymerization of ethylene and propylene catalyzed by vanadium(IV) complexes containing monodentate amide ligands. Vanadium(V) complexes bearing chelating aryloxides have been shown to be highly active (up to <sc>144400 kg mol^–1 h^–1)</sc> in copolymerization of ethylene with propylene, affording ethylene-propylene copolymers with low propylene content (less than 15%(mol)). Ethylene-propylene copolymers with high propylene content (more than 30%(mol)) could be prepared by vanadium complexes containing monodentate or bedentate ligands. It is interesting to note that quasi-living copolymerization of ethylene with propylene was realized by using vanadium(V) complexes containing NHC ligand and ethylene-propylene copolymers with ultrahigh molecular weight and narrow molecular weight distribution were obtained. In conclusion, the vanadium complex catalysts have displayed good catalytic behavior towards the copolymerization of ethylene with α-olefins. The vanadium complexes discussed here may be an inspiration for future work in the development of vanadium complex catalyst with high catalytic activity and high comonomer incorporation for copolymerization of ethylene with α-olefins.

Effect of aryl orientation on olefin polymerization in iminopyridyl catalytic system

Herein, synthesis and characterization of a series of bulky aryl substituted iminopyridyl ligands and the corresponding palladium and nickel complexes are described in detail. The as-synthesized palladium complexes show moderate activity in the ethylene polymerization and generate highly-branched oligoethylene or polyethylene with low molecular-weights. Meanwhile, the prepared palladium complexes perform a high degree of comonomer incorporation in ethylene/methyl acrylate (MA) or ethylene/acrylic acid (AA) copolymerizations. Exclusively, Pd3 catalyst exhibits a high comonomer incorporation and provides copolymers with an appreciable molecular weight for ethylene/MA (8.4 MA%, 12937 g mol−1) and ethylene/AA (8.9 AA%, 12552 g mol−1). The corresponding nickel complexes are all highly active in ethylene polymerization and produce branched oligoethylene and/or polyethylene with low to moderate molecular weights. Intriguingly, the orientation of aryl substituents plays a decisive role in the molecular weight of the attained polymer or copolymer under the performed reaction conditions.

Homopolymerization of styrenic monomers and their copolymerization with ethylene using group 4 non‐metallocene catalysts

AbstractHomopolymerization of styrenic monomers (St, p‐Me‐St, p‐tBu‐St, p‐tBuO‐St) and their copolymerization with ethylene, with the use of [(tBu2O2NN′)ZrCl]2(μ‐O) (1) and (tBu2O2NN′)TiCl2 (2), where tBu2O2NN′ = Me2N(CH2)2N(CH2‐2‐O−‐3,5‐tBu2‐C6H2)2, is explored in the presence of MMAO and (iBu)3Al/Ph3CB(C6F5)4. The ethylene/styrenic monomers copolymerization with 1/MMAO produces exclusively copolymers with high activity and good comonomer incorporation whereas the other catalytic systems yield mixtures of copolymers and homopolymers. The use of p‐alkyl styrene derivatives instead of styrene raises the catalytic activity, comonomer incorporation and molecular weights of the copolymers. Complex 2 exhibits higher activity in homopolymerization of styrenic monomers than 1 irrespective of the kind of the activator employed. A clear dependence is observed for the molecular weight and catalyst activity against the kind of the styrenic monomer. The obtained polymers were atactic and only the complex 2, when activated by MMAO, promoted the highly syndiospecific polymerization of p‐Me‐St and p‐tBu‐St. Poly(p‐tBuO‐St) exhibits fiber‐forming properties.

Ethylene homopolymerization and copolymerization with 1-hexene and 1-octene catalyzed by titanium(IV) dichloride TADDOLate complex activated with MAO

The synthesis and olefin polymerization behavior of a new TADDOL-based Ti(IV) complex, (4R,5R)-2,2-dimethyl-??,??,?????,?????-tetrakis[bis-(3,5-trifluoromethyl)phenyl]-1,3-dioxolane-4,5-dimethanolato-titanium(IV) dichloride, are described. Upon activation with MAO, this complex polymerized ethylene, producing ultra-high molecular weight linear polyethylene (UHMWPE) with activities up to 4500 kg mol (Ti)???1 [C2H4]???1 h???1 atm???1 and molecular weights up to 3.25????????106. The optimal temperature for UHMWPE synthesis was 50 ??C. This complex is also capable of copolymerizing ethylene with 1-hexene and 1-octene, giving high molecular weight copolymers with ??-olefin incorporation up to 7.8%. The copolymers, obtained with a different ratio of comonomers, are statistical, according to the analysis of the 13C NMR spectra. The reaction parameters that influenced the copolymerization behavior, such as comonomer concentration, reaction temperature and [Al]/[Ti] molar ratio, are examined in detail. Furthermore, high catalytic activities up to 12,531 kg mol(Ti)???1 [C2H4]???1 h???1 atm???1 were observed in copolymerization of ethylene and 1-hexene or 1-octene with the 2/MAO catalytic system. The obtained copolymers possess high molecular weights (Mw???=???1.4????????106???ethylene/1-hexene and 1.86????????106???ethylene/1-octene) with broad MWD (Mw/Mn???=???3.04???8.23) and high comonomer incorporation degrees (up to 6.2 mol% of 1-hexene and 7.8 mol% of 1-octene). Depending on the synthesis conditions, it is possible to form both a statistical copolymer and a block copolymer.

Efficient Addition Polymerization of Norbornene with Polar Norbornene Derivatives by Neutral Nickel(II) Catalysts

A series of nickel complexes {4a: [(2,6-iPr2C6H3)N=CHC16H12O]Ni(Me)(Py), 4b: [(2,6-iPr2C6H2OCH3)N=CHC16H12O]-Ni(Me)(Py), 4c: [(2,6-iPr2C6H2Cl)N=CHC16H12O]Ni(Me)(Py), and 4d: [(2,6-iPr2C6H2CF3)N=CHC16H12O]Ni(Me)(Py)} based on β-ketiminato ligands bearing various electron-donating or electron-withdrawing substituents on the para-position of the aniline group were synthesized and unambiguously characterized. The X-ray crystallographic analysis showed that complexes 4b and 4d adopted a near-square-planar geometry, and the anilines bearing a para-OMe or −CF3 group were found to situate on the axial position of the metal center. All complexes exhibited high activities up to 1.25 × 107–1.35 × 107 gPNB·molNi−1·h−1 toward norbornene (NBE) addition polymerization (conversion > 91.2% in 2 min) under low loading of B(C6F5)3 (B/Ni = 3) at 30 °C, affording polymers with high molecular weight up to 2.54 × 106–3.18 × 106. Different levels of decrease in catalytic activities could be observed for all catalysts as the reaction temperature increased; 4d bearing a strong electron-withdrawing −CF3 group showed the highest activity at 70 °C, while others exhibited notable decrease in catalytic activity with the raise in reaction temperature. Complexes 4a–4d showed remarkable tolerance to polar groups and could efficiently promote the copolymerization of NBE with its polar derivatives, including NBE bearing small acetate and hydroxyl group, as well as bulky oligomers, yielding copolymers with high functional NBE incorporations. Novel NBE copolymers with high functional comonomer incorporations and improved solubility were obtained in high yields.

Homo- and Copolymerization of Ethylene with Norbornene Catalyzed by Vanadium(III) Phosphine Complexes.

Herein, we report the homo- and co-polymerization of ethylene (E) with norbornene (NB) catalyzed by vanadium(III) phosphine complexes of the type VCl3(PMenPh3-n)2 [n = 2 (1a), 1 (1b)] and VCl3(PR3)2 [R = phenyl (Ph, 1c), cyclohexyl (Cy, 1d), tert-butyl (tBu, 1e)]. In the presence of Et2AlCl and Cl3CCOOEt (ETA), 1a–1e exhibit good activities for the polymerization of ethylene, affording linear, semicrystalline PEs with a melting temperature of approximately 130 °C. Mainly alternating copolymers with high comonomer incorporation were obtained in the E/NB copolymerization. A relationship was found between the electronic and steric properties of the phosphine ligands and the catalytic performance. Overall, the presence of electron-withdrawing ligand substituents increases the productivity, complexes with aryl phosphine (weaker σ–donor character) exhibiting a higher (co)polymerization initiation rate than those with alkyl phosphines (stronger σ–donor character). Steric effects also seem to play a key role since 1d and 1e, having large size phosphines (PCy3 θ = 170° and PtBu3 θ = 182°, respectively) are more active than 1a (PMe2Ph θ = 122°). In this case, the larger size of PtBu3 and PCy3 likely compensates for their higher donor strength compared to PMe2Ph.

Synthesis and characterization of chromium complexes 2-Me4CpC6H4CH2(R)NHCrCl2 and their catalytic properties in ethylene homo- and co-polymerization.

A series of new half-sandwich secondary amine-coordinated dichlorochromium complexes chelated by 2-(tetramethylcyclopentadienyl)benzylamine ligands, 2-Me4CpC6H4CH2(R)NHCrCl2 [R = iPr (1), Cy (2), Ph (3), 4-MePh (4), 2,6-Me2Ph (5), 2,6-Et2Ph (6)], have been synthesized from the reactions of CrCl3(THF)3 with the dilithium salts of the corresponding ligands in THF, followed by the addition of 1/2 eq. of H2O to the reaction mixtures. The isolated yields of the chromium complexes were found to increase with the increase in the amount of H2O introduced and reach the highest values (66-76%) when 1/2 eq. of H2O is added. Attempts to isolate the 2-(tetramethylcyclopentadienyl)benzylamidochromium complexes, 2-Me4CpC6H4CH2(R)NCrCl, were not successful. The new dichlorochromium complexes were characterized by IR, 1H NMR, EPR, and UV/Vis spectroscopy and elemental analyses, and the molecular structures of complexes 1, 5 and 6 were determined by X-ray crystallography. The X-ray crystallographic analysis reveals that these chromium complexes possess a three-legged piano-stool geometry with the amine N atom in a mitered six-membered chelating ring and the two chloride atoms as the legs. Upon activation with AlR3 and Ph3CB(C6F5)4, complexes 1-6 exhibit reasonable catalytic activity for ethylene polymerization and copolymerization with 1-hexene, producing polyethylenes with moderate to high molecular weights and poly(ethylene-co-1-hexene)s with moderate comonomer incorporation which are typical linear low-density polyethylenes (LLDPE). Complex 4 was found to show higher catalytic activity for ethylene homo- and co-polymerization than other complexes under similar conditions, while complex 3 produced poly(ethylene-co-1-hexene)s with the highest comonomer incorporation.

Catalyst Nuclearity Effects on Stereo- and Regioinduction in Pyridylamidohafnium-Catalyzed Propylene and 1-Octene Polymerizations

In comparison to monometallic controls, bimetallic olefin polymerization catalysts often exhibit superior performance in terms of higher polyolefin Mw, higher comonomer incorporation, and higher polar comonomer tolerance. However, using cooperating catalyst centers to modulate stereoselectivity in α-olefin polymerizations is relatively unexplored. In this contribution, the monometallic Hf(IV) complex, L1-HfMe2 (catalyst A, L1 = 2,6-diisopropyl-N-{(2-isopropylphenyl)[6-(naphthalen-1-yl)pyridin-2-yl]methyl}aniline), and homo-bimetallic Hf(IV) complexes, L2-Hf2Me5 (catalyst B) and L2-Hf2Me4 (catalyst C) (L2 = N,N′-{[naphthalene-1,4-diylbis(pyridine-6,2-diyl)]bis[(2-isopropylphenyl)methylene)]bis(2,6-diisopropylaniline}), are activated with Ph3C+B(C6F5)4– and investigated in propylene and 1-octene homopolymerizations. In propylene polymerizations, the conformationally flexible catalyst B-derived bimetallic dicationic catalyst produces higher Mw polypropylene (up to 7.8×), higher total stereo- and regiodefect densities (up to 3.5×), and lower Tm (by as much as ∼14 °C) versus the monometallic catalyst A-derived control. In 1-octene polymerizations, the conformationally flexible catalyst B-derived bimetallic dicationic catalyst induces greatly reduced isotacticity (23% reduction in [mmmm]) versus the catalyst A-derived monometallic control ([mmmm] > 99%). Interestingly, conformationally flexible catalyst B-derived cationic bimetallic Hf catalysts are also known to undergo rapid intramolecular/intermetal methyl exchange and to exhibit strong Hf···Hf cooperative enchainment effects in ethylene homo- and copolymerizations. Steric effects and intramolecular intermetal chain transfer likely both contribute to the increased isotactic polyolefin stereo- and regiodefect content.

Synthesis of silicon-functionalized polyolefins by subsequent cobalt-catalyzed dehydrogenative silylation and nickel-catalyzed copolymerization

Metal catalyzed olefin hydrosilylation and metal mediated olefin polymerization are both of great academic and industrial importance. In this article, these two aspects are combined to prepare silicon-functionalized polyolefin materials. First, pyridine-diimine cobalt-catalyzed dehydrogenative silylations of various terminal olefins with alkylsilanes lead to the formation of a variety of allylsilanes at high yields. Then, the allylsilanes are copolymerized with ethylene using an α-diimine nickel catalyst, leading to the formation of branched polyolefins with high molecular weight and moderate comonomer incorporation. This subsequent catalytic process is an efficient strategy for the synthesis of silicon-functionalized polyolefins using widely available and inexpensive starting materials.

Facile, Efficient Copolymerization of Ethylene with Norbornene-Containing Dienes Promoted by Single Site Non-Metallocene Oxovanadium(V) Catalytic System.

Non-metallocene oxovanadium(V) complexes bearing either [ONNO]-type amine pyridine bis(phenolate) ligands or [ONN]-type amine pyridine phenolate ligands were employed as efficient catalysts to copolymerize ethylene with several unsymmetrical norbornene-containing dienes, such as 5-vinyl-2-norbornene (VNB), 5-ethylidene-2-norbornene (ENB) or dicyclopentadiene (DCPD), producing copolymers with high comonomer incorporations (VNB: 33.0 mol %; ENB: 30.4 mol %; DCPD: 31.6 mol %, respectively) and high molecular weight (VNB: 86.4 kDa; ENB: 256 kDa; DCPD: 86.4 kDa, respectively). The enchainment of the dienes was proven to be exclusive of vinyl-addition via the C=C double bond of the norbornene ring while the other double bond was retained near the backbone without crosslinking. During the copolymerization of ethylene with ENB, a positive ‘comonomer effect’ was observed. The catalytic activities of the catalysts as well as the molecular weights and comonomer incorporations of the resultant copolymers could be tuned within a wide range by varying the structures of the catalysts and copolymerization conditions. The [ONN]-type oxovanadium(V) complexes showed higher catalytic activities than those of [ONNO]-type oxovanadium(V) complexes, irrespective of the structure of the dienes. In addition, the dominant chain transfer pathway of the non-metallocene oxovanadium(V) catalytic system promoted copolymerization was proven to be transfer to aluminum compounds.

Direct Synthesis of Branched Carboxylic Acid Functionalized Poly(1-octene) by α-Diimine Palladium Catalysts.

In this work, we studied propylene polymerization using some α-diimine palladium catalysts with systematically varied ligand sterics. In propylene polymerization, the ligand steric effect exhibits significant variations on the catalytic activity, polymer molecular weight, and branching density. However, the regio control for the polymer microstructure is poor. Furthermore, copolymerization of 1-octene with the highly challenging and biorenewable comonomer acrylic acid was investigated. High copolymer molecular weights and high comonomer incorporation ratios could be achieved in this system. This study provides a novel access for the direct synthesis of branched carboxylic acid functionalized polyolefins.

Copolymers of Ethylene and Vinyl Amino Acidic Ester with High Molecular Weight Prepared by Non-metallocene Catalysts

Non-metallocene catalysts containing [N, Si, N, P]-type ligands based on diphenyl phosphorus-phenylamine and their derivatives were synthesized and characterized by H(13C) NMR, ESI–MS and micro analysis. They were able to catalyze copolymerization of ethylene with N-acetyl-O-(hex-5-enyl)-l-tyrosine ethyl ester after activated by methylaluminoxane (MAO). Effects of transition metal atoms (Ti, Zr and Hf), ligand structures and polymerization conditions were investigated. The structures and properties of the obtained polymers were characterized by FT-IR, 13C NMR, GPC and DSC. The results indicated that the obtained copolymers had high weight average molecular weight of 2.70 × 105 g/mol and high comonomer incorporation rate of 23.07 wt% within the copolymer chain. The melting temperature of the copolymer was up to 138.6 °C higher than that of the polyethylene.

Copolymerization of Ethylene and Vinyl Amino Acidic Ester Catalyzed by Titanium and Zirconium Complexes

A series of titanium and zirconium complexes with ligands based on di-isopropyl phosphorus-phenylamine and their derivatives were synthesized and characterized. These catalysts were utilized to catalyze the copolymerization of ethylene with N-acetyl-O-(dec-9-enyl)-L-tyrosine ethyl ester with high catalytic activity of 6.63 × 104 g P (mol Ti)−1 h−1 after activation by methylaluminoxane (MAO). The effects of ligand structure, metal atoms (Ti, Zr) and polymerization conditions were investigated in detail. The obtained polymers were characterized by 13C-NMR, DSC, FT-IR, and GPC. The results showed that the obtained copolymer had a high comonomer incorporation rate of 2.56 mol % within the copolymer chain. The melting temperature of the copolymer was up to 138.9 °C, higher than that of the obtained homopolyethylene.