Copolymerization of ethylene and cyclopentene with bis(β-enaminoketonato) titanium complexes†

The copolymerizations of ethylene and cyclopentene with bis(β-enamino-ketonato) titanium complexes ([(Ph)NC(R2)CHC(R 1 )O] 2 TiCl 2 ; R 1 = CF 3 and R 2 = CH 3 for 1a, R 1 = Ph and R 2 = CF 3 for 1b; and R 1 = t-Bu and R 2 = CF 3 for 1c} activated with modified methylaluminoxane (MMAO) as a cocatalyst were investigated. High-molecular-weight copolymers with cis-1,2-cyclopentene units were obtained. The catalyst activity, cyclopentene incorporation, polymer molecular weight, and polydispersity could be controlled over a wide range through the variation of the catalyst structure and reaction parameters, such as the Al/Ti molar ratio, cyclopentene feed concentration, and polymerization reaction temperature. The complex 1b/MMAO catalyst system exhibited the characteristics of a quasi-living ethylene polymerization and an ethylene-cyclopentene copolymerization and allowed the synthesis of polyethylene-block-poly(ethylene-co-cyclopentene) diblock copolymer.

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