Synthesis of Allyl-Terminated Syndiotactic Polypropylene: Macromonomers for the Synthesis of Branched Polyolefins

Catalytic synthesis of functionalized (polar and non-polar) polyolefin block copolymers

Herein, we report a methodology for the synthesis of polyolefin containing block-copolymers using a catalytic postpolymerization modification strategy.

Herein, we report a methodology for the synthesis of polyolefin containing block-copolymers using a catalytic postpolymerization modification strategy. The most common polyolefin grades are converted into macroinitiators using a cross-metathesis reaction. These functionalized polyolefins are then used to initiate living: coordinative ring opening polymerization of lactide, anionic ring opening polymerization of epoxide, and radical polymerization of styrene to yield the corresponding block copolymers. The high activity of the catalysts employed in the different steps offers improved practicality for scalable synthesis.

Titanium(IV) catalysts with ancillary imino-spiroketonato ligands: synthesis, structure and olefin polymerization

New titanium(IV) complexes having two bidentate β-iminoethyl-spiro[4,5]decan-6-onato ligands with various N-aryl substituents have been synthesized. X-ray crystal structure analysis reveals that these titanium complexes all exhibit a C2-symmetric conformation with a distorted octahedral geometry, although the specific orientation of the ligands around the titanium center varies with the identity of the N-aryl moiety. Upon activation with methylaluminoxane (MAO), these complexes catalyze the polymerization of ethylene and propylene. In the case of ethylene, most complexes exhibit the characteristics of a living polymerization between 0 °C and 25 °C, producing polyethylenes with narrow molecular weight distributions and number average molecular weights up to 100,000 g/mol. Depending on the N-aryl substituents, polymerizations of propylene result in products with tacticity ranging from slightly syndiotactic to slightly isotactic.

Titanium and Zirconium Complexes with Non-Salicylaldimine-Type Imine–Phenoxy Chelate Ligands: Syntheses, Structures, and Ethylene-Polymerization Behavior

New Ti and Zr complexes that bear imine-phenoxy chelate ligands, [{2,4-di-tBu-6-(RCH=N)-C6H4O}2MCl2] (1: M = Ti, R = Ph; 2: M = Ti, R = C6F5; 3: M = Zr, R = Ph; 4: M = Zr, R = C6F5), were synthesized and investigated as precatalysts for ethylene polymerization. 1H NMR spectroscopy suggests that these complexes exist as mixtures of structural isomers. X-ray crystallographic analysis of the adduct 1HCl reveals that it exists as a zwitterionic complex in which H and Cl are situated in close proximity to one of the imine nitrogen atoms and the central metal, respectively. The X-ray molecular structure also indicates that one imine phenoxy group with the syn C=N configuration functions as a bidentate ligand, whereas the other, of the anti C=N form, acts as a monodentate phenoxy ligand. Although Zr complexes 3 and 4 with methylaluminoxane (MAO) or [Ph3C]+ [B(C6F5)4]-/AliBu3 displayed moderate activity, the Ti congeners 1 and 2, in association with an appropriate activator, catalyzed ethylene polymerization with high efficiency. Upon activation with MAO at 25 degrees C, 2 displayed a very high activity of 19900 (kg PE) (mol Ti)(-1) h(-1), which is comparable to that for [Cp2TiCl2] and [Cp2ZrCl2], although increasing the polymerization temperature did result in a marked decrease in activity. Complex 2 contains a C6F5 group on the imine nitrogen atom and mediated nonliving-type polymerization, unlike the corresponding salicylaldimine-type complex. Conversely, with [Ph3C]+ [B(C6F5)4]-/AliBu3 activation, 1 exhibited enhanced activity as the temperature was increased (25-75 degrees C) and maintained very high activity for 60 min at 75 degrees C (18740 (kg PE) (mol Ti)(-1) h(-1)). 1H NMR spectroscopic studies of the reaction suggest that this thermally robust catalyst system generates an amine-phenoxy complex as the catalytically active species. The combinations 1/[Ph3C]+ [B(C6F5)4]-/AliBu3 and 2/MAO also worked as high-activity catalysts for the copolymerization of ethylene and propylene.