| Abstract: | By choosing a proper agitator and reinforcing its stirring shear, powdery syndiotactic polystyrene (sPS) is prepared in a bulk precipitation process with two homogeneous metallocene catalyst systems [Cp*TiX3/MAO/TIBA (X = Cl or OPhOMe)]. A full‐range kinetics study of the heterogeneous polymerization is performed in detail to produce this kind of powdery sPS in an industrial process. A typical curve of conversion versus time takes an S shape and an obvious acceleration phenomenon occurs in the middle stage of the polymerization, although the polymer–monomer gel is avoided. The viscous‐average molecular weight of sPS goes through a peculiar increasing–decreasing–increasing change during the bulk polymerization process. These phenomena are viewed in terms of the two‐phase polymerization mechanism and the overheating in particles during polymerization. The influence of the metallocene catalyst type and concentration, MAO/Ti ratio, triisobutyl aluminum (TIBA)/Ti ratio, and polymerization temperature on the polymerization kinetics are investigated. TIBA has dual effects on the polymerization. A small amount of TIBA in the catalyst system promotes polymerization, but more TIBA leads to a low molecular weight sPS. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2635–2643, 2002 |
