Synthesis of highly syndiotactic polymers by discrete catalysts or initiators

Progress in the synthesis of highly stereoregular polymers with syndiotacticity ≥90% from an array of monomer substrates is surveyed, with a focus being placed on the use of syndiospecific discrete catalyst or initiator systems also exhibiting high activity and efficiency in the polymerization reactions. The monomer scope encompasses nonpolar α-olefins (propylene, styrene, and higher α-olefins), conjugated diolefins, bicyclic olefins, polar conjugated olefins (acrylic monomers such as methacrylates and (meth)acrylamides), and cyclic esters (lactides and β-lactones), while the polymerization catalysts or initiators enabling such syndiospecific polymerizations cover those discrete molecular complexes of main-group, early transition, and lanthanide metals. Several free-radical polymerization systems capable of producing highly syndiotactic polymers are also highlighted.