Uniting Group-Transfer and Ring-Opening PolymerizationBlock Copolymers from Functional Michael-Type Monomers and Lactones
journal contributionposted on 29.11.2021, 21:29 by Moritz Kränzlein, Thomas M. Pehl, Friederike Adams, Bernhard Rieger
Herein, the consecutive group-transfer polymerization (GTP) of the Michael-type monomer 2-vinylpyridine (2VP) and ring-opening polymerization (ROP) of ε-caprolactone (CL) or (−)-menthide (M) using a monometallic and a bimetallic 2-methoxaminethylamino-bis(phenolate) yttrium catalyst for the synthesis of AB- and BAB-type block copolymers (P2VP-b-PCL and P2VP-b-PM) are reported. Using the more demanding (−)-menthide, further insights into the catalytic nature of this combinatorial polymerization approach were gained using a kinetic copolymerization approach. These investigations revealed a living-type polymerization, for the initial GTP sequence as well as the subsequent ROP. To show the influence of the coordination strength of the monomers to the metal center, the addition sequence is alternated, uncovering a lower coordination strength of Michael-type monomer 2VP to the metal than that of lactones. Quenching of the active propagating chain end during ROP chain growth showed a coordination–insertion mechanism for the polymerization of CL and M initiated by an acyl-oxygen cleavage of lactones by the active P2VP chain. The AB- and BAB-type block copolymers of P2VP with PCL or PM showed the formation of precisely defined micelles in an acidic medium, and thermal transitions of the copolymers were shown to be microphase separation-influenced.
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precisely defined micelleskinetic copolymerization approachbis ( phenolatetype monomer 2lower coordination strengthdemanding (−)- menthidecombinatorial polymerization approachactive p2vp chaintype monomer 2vptype block copolymersinitial gtp sequencecoordination strength(−)- menthidetype polymerizationbimetallic 2addition sequencetype monomersyttrium catalystuniting groupthermal transitionspm showedp2vp -<oxygen cleavageopening polymerizationmicrophase separationinvestigations revealedconsecutive groupcatalytic natureb </acidic medium>- pm