Synthesis of Chain‐End Functionalized Polyolefins with a Bis(phenoxy imine) Titanium Catalyst

Abstract

AbstractPolyethylenes and highly syndiotactic poly(propylene)s possessing chain end hydroxyl groups were synthesized by living polymerizations using L2TiCl2 [1, L: C6F5NCH(2OC6H33tBu)]/MAO and functionalized α‐olefins, H2CCH(CH2)nY [2; YOAlMe2, n = 4 (2a); YOSiMe3, n = 9 (2b)]. Because the primary insertion of 2 to a cationic species L2Ti+Me (3) derived from 1/MAO is much faster than the successive secondary insertion of 2, addition of an equimolar amount of 2 to 3 resulted in the quantitative formation of L2Ti+CH2CH(Me)(CH2)nY [4; YOAlMe2, n = 4 (4a); YOSiMe3, n = 9 (4b)]. These cationic species 4 served as functionalized initiators for the living polymerization of both ethylene and propylene and afforded polyolefins having extremely narrow molecular weight distributions and a hydroxyl group at the initiating chain end. The terminating chain end of the syndiotactic poly(propylene)s was also functionalized by adding an excess amount of 2b as a chain end capping agent to the living L2Ti–polymeryl species. Due to much slower insertion of the second molecule of 2b relative to the first one, the obtained polymers were end capped quantitatively by a single molecule of 2b. Telechelic syndiotactic poly(propylene)s were successfully synthesized through a living polymerization initiated by 4b and an end capping using 2b.magnified image