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 Et 2 SO 4 , (S)‐1‐( N ‐phenyl‐carbamoyl)‐2‐methylaziridine gave an oligomer with a structure of [CH 2 CHCH 3 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 Et 2 SO 4 , 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.