Early Transition Metal Catalysis for Olefin-Polar Monomer Copolymerization.

Introducing polar functional groups into widely used polyolefins can enhance polymer surface, rheological, mixing, and other properties, potentiallly upgrading polyolefins for advanced, value-added applications. The metal catalyst-mediated copolymer-ization of non-polar olefins with polar comonomers represents the seemingly most straightforward, atom- and energy-efficient approach for synthesizing polar functionalized polyolefins. However, electrophilic early transition metal (groups 3 and 4)-catalyzed processes which have achieved remarkable success in conventional olefin polymerizations, encounter severe limitations here, associated with the Lewis basicity of the  polar co-monomers. In recent years, however, new catalytic systems have been developed and successful strategies have emerged. In this minireview, we summarize the recent progress in early transition metal polymerization catalyst development, categorized by the catalytic metal complex and polar comonomer identity. Furthermore, we discuss advances in the mechnistic understanding of these polymerizations, focusing on critical challenges and strategies that mitigate them.