Aqueous Emulsion Homo- and Co-polymerization of 1,3-Dienes and Styrene using Cp2TiCl2 as catalyst

1,3-Butadiene and isoprene are tested in aqueous emulsion homo-polymerization by using bis cyclopentadienyl titanium dichloride (Cp2TiCl2) as active catalytic precursor. Copolymerizations of the same monomers with styrene are also performed. Cp2TiCl2, that have been already used for the production of atactic polystyrene, shows low activity in homopolymerization of conjugated dienes, while better performance are instead obtained in co-polymerization. Both homopolymers, polybutadiene and polyisoprene, present similar microstructures. Polymer chains are formed by the majority of 1,4-trans units and, in minor amount, by 1,4-cis and 1,2 (3,4 in the case of isoprene) units. All co-polymers present a statistic distribution with atactic polystyrene sequences and, 1,4-trans, 1,4-cis, and 1,2 (3,4 in the case of isoprene) diene units. Co-polymerization activity values and the percentage of diene inserted units are strictly correlated to reaction mixture composition. Co-polymer molecular weights are substantially lower than those detected for styrene homopolymer and similar to those detected for polybutadiene and polyisoprene. Depending on co-polymer composition, glass transition temperatures present values between those polystyrene and polydienes.