Syntheses and characterizations of polypropene,polystyrene and their block copolymers with titanocene catalysts

Pentamethylcyclopentadienyltitanium tribenzyloxide, Cp^*Ti(OBz)₃, was used as the catalyst precursor for polymerizations of propene and styrene. The titanocene catalyst affords atactic polypropene and syndiotactic polystyrene with high activities in the presence of methylalumimoxane (MAO). Block copolymerization of propene and styrene was carried out in the presence of Cp^*Ti(OBz)₃/MAO catalyst system by the means of external addition of triisobutylaluminum (TIBA) and sequential monomer feed. The copolymerization product is mainly a mixture of atactic polypropene(aPP) and syndiotactic polystyrene(sPS) homopolymers and aPP-b-sPS block copolymers, which can be separated into fractions with successive extraction with boiling methylethyl ketone(MEK), heptane, tetrahydrofuran(THF), and chloroform. Studies on thermal properties showed that rubbery phases and crystalline regions both appear in the block copolymer at the room temperature and that aPP-b-sPS block copolymer has better toughness than sPS.