Syndiotactic polystyrene catalytic systems

Highly syndiotactic polystyrene (SPS) was synthesized using a homogeneous catalytic system using a titanium compound and methylaluminoxane or borate [1]. The detailed syndiospecific polymerization of styrene is described in the previous chapter. 

Atactic polypropene has been synthesized with homogeneous catalytic systems based on mono-Cp trialkoxo titanium complexes activated by MAO.951 Syndiotactic polystyrene has been synthesized with different mono-Gp trialkoxo titanium derivatives activated by MAO and AlMe3, and the catalytic efficiency has been compared with bis-Cp titanium catalysts.952 The titanium ligands affect both catalytic activity and stereoregularity of the polypropylene obtained. For the CpTi(OPrn)3/MAO system, factors influencing the propylene polymerization, such as temperature, Al/Ti molar ratio, and monomer pressure, have been studied. 

Yang et al. examined rare earth coordination catalysts. The Nd(naph)3/ y4/(fBu)3 catalyst system was found to produce syndiotactic-rich polystyrene [8]. They proposed that the catalytically active species might be an ionic complex because the addition of CCI4 increased the catalytic activity. 

Syndiospecific polystyrene is also produced using SiOi-supported Ti(OC4Hg)4 with MAO, and a Si02-supported reacted mixture of Ti(OC4H9)4 and MAO (Table 2.9) [28]. The syndiotacticity of the polymers with both catalysts was almost 100%. The catalytic activity is independent of the Al/Ti molar ratio for this supported catalyst. The heterogeneous -SiO(Ti(OC4H9)3) species is more stable against reduction by MAO than the active species in the soluble system. 

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