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 cyclopentadienyltitanium trichloride-methylaluminoxane (CpTiCl3-MAO), are investigated. The reactivity ratios as well as the reactivities of the different monomers in homopolymerization are tentatively correlated to a possible polymerization mechanism. A qualitative explanation of the reactivity of different monomers in homo- and copolymerization is achieved by considering the nucleophilicity of the monomers and the electrophilicity of the active species. The latter is affected by the nature of the bond between the active Ti and the last unit of the growing chain end. The block copolymerization of ethylene with styrene is also tentatively explained by considering that the more the active species are electrophilic the less they should be selective toward monomers of different nucleophilicity.