Copolymerization of ethene with styrene using methylaluminoxane-activated bis(phenolate) complexes

Ethene was copolymerized with styrene using different titanium bis(phenolate) complexes [R1(4,6-R2C6H2-O)2]TiX2 (R1 = CH2, C2H4, S, SO; R2 = CH3, t-Bu; X = Cl, O(i-Pr)) activated with methylaluminoxane. The influence of ligand substitution pattern and polymerization conditions on catalyst activity, polymerization kinetics, styrene incorporation, molecular mass, and copolymer microstructure was investigated. Catalyst activity increased with decreasing styrene concentration and was affected by the type of the bridging group R1 with an activity rating of R1 = S > SO > C2H4. The opposite trend was observed for styrene incorporation where R1 = C2H4 gave the highest styrene content. Polymerization kinetics primarily depended upon complex structure and was only marginally influenced by polymerization conditions. As a rule, styrene contents of more than 90 mol % in the monomer feed were needed to achieve more than 20 mol % styrene incorporation in the copolymer. Copolymerization parameters were calculated for eth...