In this work, a redox-active bis(imino)pyridine iron alkoxide complex was used for the controlled polymerization of N-carboxyanhydrides (NCAs), which was leveraged for block copolymerizations of NCAs and other monomers. When the catalyst was in its reduced form, it was able to catalyze the sequential polymerization of cyclic esters and NCAs. Thus, poly(ester-b-amides) can be accessed in one-pot using sequential addition of monomers to make di-block copolymer and even tri-block copolymers if diol initiators are used for telechelic polymerizations. Oxidation of the iron complex resulted in the complete deactivation of the complex for NCA polymerization, but allowed for the polymerization of cyclohexene oxide. Activity for the polymerization of NCAs can be restored by reducing the iron catalyst. Using the orthogonal reactivity of the catalyst in its two oxidation states, poly(amide-<i>b-</i>ethers) were synthesized by changing the oxidation states of the iron catalyst <i>in situ</i>. The above-mentioned method allowed for the facile synthesis of block copolymers of polyamides, which can be challenging to synthesize with a single catalyst system without end-group functionalization of macromolecular initiators.

Synthesis of block copolymers of polyamides through ring-opening polymerization catalyzed by redox-switchable iron alkoxide complexes

2019 Fall National Meeting

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