Spontaneous alternating copolymerization of aziridines with tosyl isocyanate toward polyureas

We report a new synthetic approach toward cyclic polyureas through alternating copolymerization of aziridines with tosyl isocyanate. Aziridines (ethyleneimine, and (S)-2-benzylaziridine) react with tosyl isocyanate spon-taneously in the absence of any catalyst to produce polyureas. The obtained polyureas exhibit an alternating structure as determined by NMR and MALDI-TOF MS analysis. MALDI-TOF analysis indicates that the synthe-sized polyureas are cyclic. A spontaneous zwitterionic copolymerization mechanism is proposed. DFT calcula-tions reveal that the copolymerization of tosyl isocyanate with ethyleneimine is more kinetically and thermodynamically favored than 2-benzylaziridine.

Automated summary

We report a new synthetic approach for cyclic polyureas through alternating copolymerization. Aziridines react with tosyl isocyanate spontaneously to produce polyureas with an alternating structure. The synthesized polyureas are found to be cyclic. Calculations indicate that the copolymerization of tosyl isocyanate with ethyleneimine is more favorable kinetically and thermodynamically compared to 2-benzylaziridine.