Norbornadiene homopolymerization and norbornene/norbornadiene/1-octene terpolymerization by ansa-fluorenylamidotitanium-based catalysts

Abstract

ansa-Fluorenylamidotitanium complexes Me₂Si(Flu)(N^tBu)TiMe₂ (1) and Me₂Si(2,7-^tBu₂Flu)(N^tBu)TiMe₂ (2) were used as precatalysts for the homopolymerization of norbornadiene (NBD) and the terpolymerization of NBD, norbornene (NB), and 1-octene (OC). In the NBD homopolymerization, catalyst 2 showed double the conversion and yielded a polymer having more than double the molecular weight compared with catalyst 1 when activated by modified methylaluminoxane (MMAO). The conversion and molecular weight were significantly increased by changing the cocatalyst from MMAO to [Ph₃C][B(C₆F₅)₄]. The conversion levels after 10 min polymerization using 2-[Ph₃C][B(C₆F₅)₄] at 25 and 0 °C were 52% and 62%, respectively. The conversion reached 82% at 0 °C after 1 h, and soluble polyNBD with a number-average molecular weight (M_n) of 34 100 was obtained. The 2-[Ph₃C][B(C₆F₅)₄] catalytic system also showed the best performance for NBD/NB/OC terpolymerization among the four combinations of precatalyst/cocatalyst and gave the terpolymer with M_n of 66 300 containing 13 mol% of NBD at 64% conversion after 10 min polymerization at 0 °C. All resulting polymers possessed good solubility, indicating that crosslinking via the NB unit derived from NBD was negligible.