Nonsymmetric N-Substituted Polyureas from Ring-Opening Copolymerization of Aziridines and Isocyanates

There is no access to directly synthesizing fully N-substituted polyureas, let alone customizing the N-substitution's sequence of polyureas. In this work,we reporta new class of fully N-substituted polyureas synthesisfrom the catalyst-free ring-opening copolymerization of aziridinesand isocyanates. Fully N-pendent functionality onpolyureas was directly achieved for the first time, and interestingly,the substitution was aligned in a nonsymmetric manner. With p-tosyl isocyanate (TSI) as the isocyanate comonomer, awide variety of N-alkyl aziridines were amenablein forming polyureas, whereas the N-substituentson aziridines open avenues to facile variation of the polyureas'nonsymmetric N-substitutions. We synthesized fivenonsymmetric N-substituted polyureas, and the obtainedpolymers had cyclic topologies. The copolymerization was proposedto proceed via a zwitterionic mechanism. We believe that our findingsprovide key implications for novel functional materials based on N-substituted polyureas.