BINARY COPOLYMERIZATIONS OF STYRENE AND CONJUGATED DIOLEFINS IN THE PRESENCE OF CYCLOPENTADIENYLTITANIUM TRICHLORIDE-METHYLALUMINOXANE

Binary copolymerizations of styrene, isoprene, butadiene and 4-methyl- 1,3-pentadiene, in the presence of the catalyst cyclopentadienyltitani um trichloride-methylaluminoxane (CpTiCl3-MAO), are investigated. The reactivity ratios as well as the reactivities of the different monomer s in homopolymerization are tentatively correlated to a possible polym erization mechanism. A qualitative explanation of the reactivity of di fferent monomers in homo- and copolymerization is achieved by consider ing the nucleophilicity of the monomers and the electrophilicity of th e active species. The latter is affected by the nature of the bond bet ween the active Ti and the last unit of the growing chain end. The blo ck copolymerization of ethylene with styrene is also tentatively expla ined by considering that the more the active species are electrophilic the less they should be selective toward monomers of different nucleo philicity.