Those effective catalyst precursors for syndiotactic styrene polymerization, Cp*Ti(OCH2–CHaCH2)3 (I), Cp*Ti(OCH2–CHaCHC6H4)3 (II),
Cp*Ti(OCH2C6H5)3 (III), Cp*Ti(OCH2C6H4OCH3)3 (IV) were synthesized, and the influence of catalyst ligands on the catalytic activity and
properties of polymer were investigated. The polymer thus obtained coupled with higher molecular weight and higher syndiotacticity determined
by GPC and 13C NMR as well as solvent extraction manners, respectively. Those catalysts promoted by methyaluminoxane (MAO) as cocatalyst
exhibited higher catalytic activity. Of all catalysts mentioned foregoing, Cp*Ti(OCH2–CHaCHC6H4)3 (II), Cp*Ti(OCH2C6H5)3/MAO (III) and
Cp*Ti(OCH2C6H4OCH3)3 (IV) catalysts showed higher activity and stability even at fairly low Al/Ti ratio of 600, and possessed excellent control
of the stereoregular insertion of monomer, exhibited a significant increase of the ratio of the propagation rates to chain transfer termination. The
kinetic and titration results also indicated that those metallocene catalysts (II), (III), and (IV) showed higher catalytic activity and produced
polymer with higher molecular weight, because of a great number of active species, and lower ratio of Ktrb
=Kp, higher ratio of Ktrb
=Ktrs which
indicate that b-H elimination was predominant.
Polymer 47 (2006) 767–773