Four kinds of ancillary ligands-O-C6 H4-X[X(P)=F

Cl

Br

I] were introduced in the design of novel monotitanocene catalysts

Cp*Ti(O-C6H4-X)3．All of the new catalysts show high activity for styrene syndiotactic polymerization．The catalytic activity of the four monotitanocene increased in the order：Cp*Ti(O-C6H4-I)3*-Ti-(O-C6H4-Br)3*Ti(O-C6H4-Cl)3*Ti(O-C6H4-F)3.The addition of triisobutylaluminium(TIBA)to the catalyst system caused a dramatic increase of s-PS yield．At 90℃

MAO/TIBA/Ti=400/200/1(molar ratio)

the catalytic efficiency of Cp*Ti(O-C6H4-F)3 is up to 3.46×106g polymer/mol·Ti·10min The polymerization activity of Cp*Ti(O-C6H4-X)3 at MAO/TIBA/Ti=400/200/1(molar ratio) is about 10 times higher than that at MAO/Ti=600(in the absence of TIBA)．The catalytic efficiency of the catalyst and the molecular weight were affected by catalyst composition

monomer concentration and polymerization temperature．The kinetics of styrene syndiotactic polymerization in toluene was also studied．