High polymerization of methyl methacrylate with organonickel/MMAO systems

Abstract

A series of nickel complexes, including Ni(acac)2, (C5H5)Ni(η3-allyl), and [NiMe4Li2(THF)2]2, that were activated with modified methylaluminoxane (MMAO) exhibited high catalytic activity for the polymerization of methyl methacrylate (MMA) but showed no catalytic activity for the polymerization of ethylene and 1-olefins. The resulting polymers exhibited rather broad molecular weight distributions and low syndiotacticities. In contrast to these initiators, the metallocene complexes (C5H5)2Ni, (C5Me5)2Ni, (Ind)2Ni, and (Me3SiC5H4)2Ni provided narrower molecular weight distributions at 60 °C when these initiator were activated with MMAO. Half-metallocene complexes such as (C5H5)NiCl(PPh3), (C5Me5)NiCl(PPh3), and (Ind)NiCl(PPh3) produced poly(methyl methacrylate) (PMMA) with much narrower molecular weight distributions when the polymerization was carried out at 0 °C. Ni[1,3-(CF3)2-acac]2 generated PMMA with high syndiotacticity. The NiR(acac)(PPh3) complexes (R = Me or Et) revealed high selectivity in the polymerization of isoprene that produced 1,2-/3,4-polymer at 0 °C exclusively, whereas the polymerization at 60 °C resulted in the formation of cis-1,4-rich polymers. The polymerization of ethylene with Ni(1,3-tBu2-acac)2 and Ni[1,3-(CF3)2-acac]2 generated oligo-ethylene with moderate catalytic activity, whereas the reaction of ethylene with Ni(acac)2/MMAO produced high molecular weight polyethylene. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4764–4775, 2000