Group-transfer polymerization of Michael-type monomers (GTP) and ring-opening polymerization of lactones (ROP) are polymerization types benefiting from catalysis mediated by homogeneous metal complexes. Applying polymerization catalysts gives advantages like tunable molecular weight with low polydispersity, stereoregularity, block copolymerization or chain-end functionalization. With emphasis on GTP and ROP, some of the most applied polymerization complexes share the same metal (e.g. yttrium or zirconium) and use similar ligand motifs such as cyclopentadienyl derivatives or bisphenolates. Yet, only little is known about combining those polymerization techniques, possibly yielding GTP-b-ROP block copolymers. Beside the pioneering work from Yasuda et al., so far this research is limited to few examples combining methyl methacrylate and some lactones. However, transferring this principle to functional Michael-type monomers such as 2-vinylpyridine (2VP) or dimethyl acrylamide and different lactones such as (-)-menthide ((-)-M) or ε-caprolactone (CL) is highly challenging as catalyst structure, choice of monomer pairs and reaction conditions are crucial parameters for obtaining controlled block copolymers. By utilizing yttrium bisphenolates, combinations of 2VP as Michael-type monomer with CL or (-)-M as lactones to AB- and BAB-type copolymers could be generated, establishing a pathway towards precisely tunable GTP-b-ROP block copolymers. While the living-type propagation of the polymerization is maintained in both steps, kinetic investigation and chain end-capping revealed a catalytic copolymerization with two different mechanisms. Due to the differences in chemical nature of the two building blocks those new materials can form pH-responsive micelles and undergo microphase-separation. These results act as detailed proof of principle of pioneering work by Yasuda et al. and further research focuses on finding novel combinations of monomers.

Pushing the limits of coordinative-anionic polymerization -linking cyclic esters and Michael-type monomers for designing block copolymers with tunable properties

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.