Functionalized Polyolefins Produced by Post-Metallocenes; High Added Value Materials, but Can They Be Produced Efficiently?

The reactivity of polar vinyl monomers, unsaturated compounds containing functional groups, depends on the presence or absence of conjugation between the C=C bond and the neighbouring unsaturated moieties or donor heteroatoms. Conjugated polar vinyl monomers (acrylates, vinyl ethers, etc.) (co)polymerize upon free-radical initiation. The reaction is widely used to produce numerous polymer materials that qualitatively differ from polyolefins in their characteristics. Copolymerization of ethylene, propylene, and higher α-olefins with nonconjugated vinyl monomers containing polar or reactive functional groups gives so-called 'functional polyolefins', that is, polymer materials with unique mechanical and rheological characteristics, increased thermal and oxidative stability, and controlled hydrophilicity. In the synthesis of functional polyolefins, only coordination polymerization, catalyzed by complex compounds of Group 4 metals, V, Sc, Ni, and Pd is effective. This review summarizes for the first time data on the (co)polymerization of polar vinyl monomers catalyzed by early transition metal complexes, discusses the current results achieved in the catalysis of copolymerization of polar vinyl monomers by Group 10 metal complexes, and considers the prospects for practical application of functional polyolefins and for organization of their industrial production.  The bibliography includes 272 references.

Coordination copolymerization of &aplpha;-olefins with non-conjugated polar vinyl monomers: current catalytic approaches and prospects for practical applications

A zirconium complex of diamine-bis(phenolate) ligand, [(tBu2O2NN’)ZrCl]2(μ-O) where (tBu2O2NN’) = Me2N(CH2)2N(CH2–2-O−-3,5-tBu2-C6H2)2, activated with (iBu)3Al/Ph3CB(C6F5)4, was for the first time used in copolymerization of ethylene with unsaturated alcohols (CH2 = CH(CH2)nCH2OH, where n = 7, 8, 3). The hydroxyl groups of comonomers were protected with R3-xAlClx (where x = 0 or 1, R = iBu, Et). In contrast to the formerly reported catalysts, the activity of this catalyst is much higher in ethylene/alkenols copolymerization than in ethylene homopolymerization and its lifetime is long. Moreover, the copolymers with high polar comonomer contents (up to 16.4 mol%, 52.3 wt%) were produced. The effects of copolymerization conditions such as comonomer/protecting agent molar ratio, comonomer concentration, ethylene pressure and reaction time on the catalyst activity and comonomer incorporation were studied. In addition, polyalkenols were synthesized by the coordination polymerization of α,ω-alkenols with the use of [(tBu2O2NN’)ZrCl]2(μ-O) and rac-Et(Ind)2ZrCl2 for reference. DSC, TG, GPC, SEM, 1H and 13C NMR, and FTIR methods were used to characterize the (co)polymerization products.

Effective copolymerization of ethylene with α,ω-alkenols and homopolymerization of α,ω-alkenols catalyzed by aminophenolate zirconium complex

To unravel the relationship between silylene-bridged metallocene catalyst structures and polymerization conditions and their effect on the performance in in-reactor functionalization of polypropylene, the behaviors of rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2/MMAO, rac-Me2Si(Ind)2ZrCl2, rac-Me2Si(2-Me-4-Ph-Ind)2HfCl2, and rac-Me2Si(Ind)2HfCl2 in propylene/aluminum alkyl-passivated 10-undecen-1-ol copolymerization were compared. Kinetic analysis revealed higher catalytic activities for zirconocenes compared to analogous hafnocenes. Both the zirconocene and hafnocene with substituted indenyl ligands afforded a higher molecular weight capability, improved stereo-selectivity, and enhanced ability to incorporate functionalized comonomers compared to their non-substituted congeners. An in-depth study of polypropylene functionalization using the best performing catalyst system, rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2/MMAO, at temperatures ranging from 40 to 100 °C, revealed a linear inversely proportional correlation of polymerization temperature with functionalized comonomer reactivity (↑Tp → ↓ r1), copolymer molecular weight (↑Tp → ↓Mn), and melting temperature (↑Tp → ↓Tm). While performing well under standard laboratory polymerization conditions, rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2/MMAO showed limited molecular weight and stereo-selectivity capabilities under high-temperature (130–150 °C) solution process conditions. Although immobilization of rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 onto silica, allowing it to be used under industrially relevant slurry and gas-phase conditions, led to an active catalyst, it failed to incorporate any functionalized comonomer. 

https://pure.rug.nl/ws/files/494695189/acs.macromol.1c02220.pdf

In-Reactor Polypropylene Functionalization─The Influence of Catalyst Structures and Reaction Conditions on the Catalytic Performance

Polyolefins with polar groups exhibited many applications as high-performance materials have been the subject of considerable research. In this study, terpolymers of ω-bromo-α-olefins with ethylene and propylene were synthesized in the presence of three multi-chelated non-metallocene titanium complexes. The structure and properties of the terpolymers were determined by 1H NMR, 13C NMR, Fourier transform infrared, differential scanning calorimetry after treatment by successive self-nucleating and annealing and wide-angle X-ray diffractograms. Furthermore, the stress–strain behaviors of the terpolymers were measured with ASTMD1708 microtensile, and the specimens were from the obtained terpolymer films. The results indicated that these catalysts were efficient for the terpolymerization. The catalytic activity was as high as 6.21 × 105 gP (molTi)−1 h−1 for terpolymerization of 11-bromo-1-undecylene with ethylene and propylene. The insertion ratio of 11-bromo-1-undecylene was up to 2.49 mol% confirmed by 1H NMR and 13C NMR. As for the terpolymers, their melting points decreased and their plasticity became weak with the incorporation of ω-bromo-α-olefins increasing. GPC results showed that the terpolymers had high weight-average molecular weight up to 2.51 × 105 g mol−1. Molecular weight distribution of the terpolymers was about 2, implying single-site mechanism for the terpolymerization, but slightly broader than that of ethylene/propylene copolymer.

Investigation on terpolymer of ethylene/propylene/ω-bromo-α-olefins catalyzed by titanium complexes

Copolymerizations of propylene with ω-alkenols (aluminum-protected 5-hexene-1-ol (AH) and 10-undecene-1-ol (AU)) and non-polar analogues (1-hexene and 1-dodecene) were conducted with a rac-[Me2Si(2-Me-4-Ph-Ind)2]ZrCl2 activated by modified methylaluminoxane. The catalytic system showed high activity for each copolymerization, of which value was independent on the comonomer used and decreased with the increase of the comonomer concentration. The comonomer content of the copolymers obtained also decreased with the increase of the comonomer concentration in each copolymer. The evaluation of the monomer reactivity ratios indicates a preference for the propylene insertion regardless of the last inserted monomer unit in growing polymer chain in all the copolymerizations. The relative reactivity of ω-alkenols was however significantly lower than that of non-polar analogues. These results suggested that the aluminum protection of polar monomer do not affect the activity of copolymerization but significantly decrease the comonomer reactivity.

/pdf/reactivity-comparison-of-o-alkenols-and-higher-1-alkenes-in-2dnwhtzf1b.pdf

Reactivity Comparison of ω-Alkenols and Higher 1-Alkenes in Copolymerization with Propylene Using An Isospecific Zirconocene-MMAO Catalyst

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Reactivity Comparison of ω-Alkenols and Higher 1-Alkenes in Copolymerization with Propylene Using An Isospecific Zirconocene-MMAO Catalyst