Janus Effect of Lewis Acid Enables One-Step Block Copolymerization of Ethylene Oxide and N-Sulfonyl Aziridine

One-step sequence-selective block copolymerization requires stringent catalytic control of monomers relative activity and enchainment order. It has been especially rare for A(n)B(m)-type block copolymers from simple binary monomer mixtures. Here, ethylene oxide (EO) and N-sulfonyl aziridine (Az) compose a valid pair provided with a bicomponent metal-free catalyst. Optimal Lewis acid/base ratio allows the two monomers to strictly block-copolymerize in a reverse order (EO-first) as compared with the conventional anionic route (Az-first). Livingness of the copolymerization facilitates one-pot synthesis of multiblock copolymers by addition of mixed monomers in batches. Calculation results reveal that a Janus effect of Lewis acid on the two monomers is key to enlarge the activity difference and reverse the enchainment order.

Automated summary

One-step sequence-selective block copolymerization requires strict catalytic control of monomer activity and enchainment order, especially for A(n)B(m)-type block copolymers from simple binary monomer mixtures. In this study, ethylene oxide (EO) and N-sulfonyl aziridine (Az) form a valid pair with a bicomponent metal-free catalyst. The optimal Lewis acid/base ratio allows the two monomers to block-copolymerize strictly in a reverse order (EO-first) compared to the conventional anionic route (Az-first). The livingness of the copolymerization enables the one-pot synthesis of multiblock copolymers by adding mixed monomers in batches. Calculation results suggest that the Janus effect of Lewis acid on the two monomers is crucial for enlarging the activity difference and reversing the enchainment order.