Dual systems combining Zn(C6F5)2 with an organic base (an amine or a phosphine) promote the controlled ring-opening polymerization of lactide and ε-caprolactone. The Lewis pairs cooperate to activate the monomers, affording well-defined high molecular weight cyclic polyesters. Efficient chain-extension gives access to cyclic block copolymers.
Recently catalytic systems combining Al, In or Zn Lewis acids with organic bases (amines, phosphines, N-heterocyclic carbenes) have been shown to efficiently promote the polymerization of lactones and polar olefins. In this frontier article, such dual approaches of polymerization catalysis are presented. Special attention is devoted to the mode of action of the dual systems and the underlying cooperative effects.
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