Copolymerization of ethylene with α-olefins and cyclic olefins catalyzed by a Ti(iv) diisopropoxy complex bearing a tridentate [O−,S,O−]-type bis(phenolato) ligand

Abstract

Ethylene (E) was copolymerized with some α-olefins [1-pentene (PEN), 1-hexene (HEX), and 4-methyl-1-pentene (4M1P)] and cyclic olefins [cyclopentene (CPE), norbornene (NB), and dicyclopentadiene (DCPD)] using the Ti(IV) thiobis(phenolate) complex [2,2′-S(4-Me,6-tBuC₆H₂O)₂]Ti(OiPr)₂ in combination with methylaluminoxane (MAO). The catalyst exhibited excellent activities (up to 10⁶ g mol_Ti⁻¹ h⁻¹). Crystalline E/α-olefin copolymers with a strong tendency for comonomer alternation were obtained with good comonomer incorporation (about 15 mol% for [Y]/[E] = 8; Y = comonomer) decreasing in the order HEX > PEN > 4M1P. Random copolymers with NB and DCPD were obtained with efficient comonomer incorporation (from 10 to 40 mol%) even for the Y/E molar ratio = 1 to 2, while the catalyst gave poor CPE incorporation. In order to collect information on the comonomer distribution in the copolymers, boiling solvent extraction was carried out and all the fractions were characterized by DSC, XRD, SEC, and NMR.