Polymerization of propylene catalyzed by α-diimine nickel complexes/methylaluminoxane: catalytic behavior and polymer properties

Abstract

α-Diimine nickel dibromide complexes of dibromo[N,N’-bis(2,6-diisopropylphenyl)-2,3-butanediimine]nickel(II) (A) and dibromo[N,N’-(phenanthrene-9,10-diylidene)bis(2,6-diisopropylaniline)]nickel(II) (B) were synthesized under controlled conditions. The catalysts A, B and mixed of 1:1 weight ratio of them (C) were activated by methylaluminoxane and were used for propylene polymerization in a semi-batch reactor. In study of the catalytic systems behavior, activities, glass transition temperature (Tg) and viscosity average molecular weight (Mv) values related to the catalyst C were between those related to the catalysts A and B under same conditions. The highest and the lowest molecular weights of the obtained polymers were produced by the catalysts B and A which were about 80,000 and 70,000 (g/mol) under same conditions, respectively. The Tg of polypropylenes produced by the catalysts was about −34 °C. The resulting polymers had similar behavior with ethylene-propylene copolymer which it could be due to formation of ethylene-type units in the polymer chain.