Syndiospecific polymerization of styrene with half-titanocene catalysts containing fluorinated phenoxy ligands

Novel half-titanocene catalysts containing fluorinated phenoxy ligands were synthesized and used for the syndiotactic polymerization of styrene in the presence of low methylaluminoxane (MAO) and triisobutylaluminum (TIBA) as cocatalysts. The influences of polymerization conditions, including temperature and Al/Ti ratio, on polymerization behaviour and the molecular weight of the resultant polymer were studied. The fluorinated half-titanocene catalysts displayed higher catalytic activity and produced syndiotactic polystyrene (sPS) with a higher molecular weight as a result of the electron-withdrawing conjugation effect of fluorinated phenoxy ligands. This effect stabilizes Ti(iii) active centers and/or enhances propagation while reducing the chain transfer rate constant.