ESR study on MgCl2-supported half-titanocene catalyst for syndiospecific polymerization of styrene

The MgCl2-supported CpTiCl3 catalysts with different Ti content were prepar ed and used for syndiospecific polymerization of styrene. These catalysts w ere investigated by means of electron spinning resonance (ESR) spectroscopy . It is found that there exist two kinds of active species in this catalyti c system. One is a specific active site and cannot be removed into the solu tion by MAO. The other one is readily removed into the solution during the interaction with MAO, and the same active site as that in the CpTiCl3-MAO h omogeneous system is formed. The MgCl2 supported CpTiCl3 catalyst was also compared with the SiO2/CpTiCl3-MAO system. The data show that the CpTiCl3 s upported on the MgCl2 surface is more difficult to be removed by MAO than t he active site immobilized on the SiO2 surface, leading to the lower activi ty of MgCl2/CpTiCl3-MAO system and lower syndiotacticity of obtained polyst yrene. (C) 1998 Elsevier Science Ltd. All rights reserved.