Spontaneous alternating copolymerization of aziridines with tosyl isocyanate toward polyureas

摘要

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.

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