Polymerization and copolymerization of styrene by Ph2Zn-Metallocene-MAO initiator systems.

Combined systems including diphenylzinc, Ph2Zn, metallocene, and methylalum inoxane, MAO, have been employed to initiate styrene polymerization. These initiator systems have been also used to initiate the copolymerization of s tyrene with p-alkylsubstituted styrenes and with cc-olefins. Both polymeriz ation and copolymerization processes depend on the nature of the metallocen e included in the initiator system, the presence of Ph2Zn, the temperature and the solvent used. Titanocenes produced syndiotactic polystyrene, s-PS, while zirconocenes gave atactic polystyrene, a-PS, with a certain content, less the 20% of s-PS. For copolymerizations the conversion to polymer was a lso influenced by the comonomer nature and its molar proportion in the init ial feed, as well as the sort of metallocene, titanocene or zirconocene inc luded.