Catalytic systems Me2SiCp*(NBuMX2)-Bu-t/(CPh3)(B(C6F5)(4)) (M = Ti, X = CH3, M = Zr, X = Bu-t) in copolymerization of ethylene with styrene

Catalytic activity of Me2SiCp*(NBuMX2)-Bu-t/(CPh3)(B(C6F5)(4)) [M=Ti, X=CH3 (1); M=Zr, X=Bu-i (2)] systems in the ethylene/styrene (E/S) feed was exam ined. Experimental data revealed high activity for the catalytic system (1) for copolymerization ethylene with styrene, whereas the system with enhanc ed catalytic activity for ethylene homopolymerization (2) was temporarily b locked in the styrene presence yielding, even at high styrene content, homo polyethylene as the final product. Properties of thus obtained polymers wer e analyzed. Catalytic system (1) occurred very sensitive to S/E ratio in th e comonomers feed. The 1.0-fold acceleration for ethylene consumption was s hown in two experimental sets conducted at S/E = 1.3 ratio, 1 bar, and 7.5 bar ethylene pressure, respectively. The consequent enhancement in S/E rati o resulted in slowing down both ethylene consumption and catalyst deactivat ion rates. Atactic polystyrene was formed at,high styrene content with the catalyst (1). Catalytic system (1) allowed design of products with the high est styrene content (20 mol %) at low ethylene pressure, moderate temperatu re, and high S/E ratio. The apparent activation energy estimated from the i nitial rates of ethylene consumption was 54.6 kJ/mol. Analysis of apparent reactivity factors (r(E) = 9 and r(S) = 0.04; r(E) x r(S) = 0.4) and C-13-N MR copolymer spectra revealed an alternating tendency of the comonomers for active center incorporation. DSC measurements showed considerable decrease of melting points and crystallinity even for copolymers with low styrene c ontent. The catalyst produced relatively high-molecular weight copolymers ( C) 1999 John Wiley & Sons, Inc.