It is critical to produce sustainable alternatives for commercialized polymer products that will address the mounting plastic waste problem. Polyolefin/polar block copolymers have already been commercialized and are a vital class of soft materials with an expanding range of applications. However, these block copolymers typically require multiple catalysts and steps to synthesize and are generally made of non-degradable materials. Cationic rare earth metal catalysts are promising in this arena as they are efficient and selective for the polymerization of these two distinctive classes of monomers. This polymerization can be carried out in a one-pot system where the monomers are added in a sequential manner that leads to block copolymer morphologies, thus eliminating the need for multiple catalysts and steps. Few cationic rare earth metal catalysts have been identified for this polymerization and the range of monomers studied is limited. Yttrium complexes with easy-to-modify ligands have been identified to show excellent rates and dispersities for the target copolymerization of olefins and polar monomers. Strategic adjustments in the steric and electronic profile of the ligand framework could provide catalysts that can handle a wider range of monomers. Alternative polar monomers such as cyclic esters or carbonates are seldom investigated but would be desirable as they add a degree of degradability to the block copolymer, allowing for the recovery of the olefin block. In addition, using bioderived olefins such as terpenes offers an exciting avenue for study, because this class of monomers has diverse structures, including acyclic, monocyclic, bicyclic, that could alleviate consumption of petroleum-based olefins. The impact of ligand properties on the rate, selectivity, and control of block copolymerization of a dynamic range of olefins and polar monomers will be discussed.

One-pot block copolymerization of olefins with degradable polar monomers using yttrium metal catalysts

ACS Spring 2022

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