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 report a new class of fully N-substituted polyureas synthesis from the catalyst-free ring-opening copolymerization of aziridines and isocyanates. Fully N-pendent functionality on polyureas 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, a wide variety of N-alkyl aziridines were amenable in forming polyureas, whereas the N-substituents on aziridines open avenues to facile variation of the polyureas' nonsymmetric N-substitutions. We synthesized five nonsymmetric N-substituted polyureas, and the obtained polymers had cyclic topologies. The copolymerization was proposed to proceed via a zwitterionic mechanism. We believe that our findings provide key implications for novel functional materials based on N-substituted polyureas.