Nonclassical urea oligomers. IV. Polymerization of (S)-1-(N-phenyl-carbamoyl)-2-methylaziridine. A synthesis of optically active crystalline oligomer with narrow molecular weight distribution

In the presence of Et₂SO₄, (S)-1-(N-phenyl-carbamoyl)-2-methylaziridine gave an oligomer with a structure of CH₂? CHCH₃? N(CONHPh)]_n. The oligomer has optically active isotactic configuration and narrow molecular weight distribution (DP ca. 8). The net polymerization behavior of the monomer and chemical property, such as absorptivity of Et₂SO₄, of the oligomer are analogous to the case of 1-(N-phenyl-carbamoyl)-aziridine. The ring opening occurs with retention of the configuration at the asymmetric carbon atom and the oligomer can be crystallized at around 90°C.