Ethylene homopolymerization and Copolymerization with 1-Hexene and 1-Octene Catalyzed by Titanium (IV) Dichloride TADDOLate Complex activated with MAOстатья
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Аннотация:The synthesis and olefin polymerization behavior of a new TADDOL-based Ti(IV) complex, (4R, 5R) -2,2-dimethyl-α,α,α',α'-tetrakis[bis-(3,5-trifluoromethyl)phenyl]-1,3-dioxolane-4,5-dimethanolato-titanium(IV) dichloride, is 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 50ºС. This complex is also capable of copolymerizing ethylene with 1-hexene and 1-octene, giving high molecular weight copolymers with α-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 12531 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.
