Propylene−Styrene Multiblock Copolymers: Evidence for Monomer Enchainment via Opposite Insertion Regiochemistry by a Single-Site Catalyst

Polymerization of propylene promoted by the post-metallocene catalyst 1 and methylaluminoxane (MAO) produces oligomers containing prevailingly unsaturated chain ends which are diagnostic of a primary (1,2) regiochemistry of insertion. The styrene polymerization in the presence of propylene produces multiblock copolymers containing long isotactic styrene sequences interrupted by short isotactic propylene strings. The microstructure of these copolymers elucidated by 13 C NMR analysis shows that the opposite regiochemistry of insertion of the two monomers is retained in the copolymerization, producing tail-to-tail and head-to-head linkages between the homopolymer blocks.