AbstractThe anionic polymerization of ϵ‐caprolactam (CL), initiated with the sodium or potassium salt of CL, was shown to be accelerated with 1‐(1‐pyrrolin‐2‐yl)‐2‐pyrrolidone(1), 1‐(1‐azacyclohept‐1‐en‐2‐yl)‐2‐pyrrolidone(2), 1‐(1‐azacyclonon‐1‐en‐2‐yl)‐2‐pyrrolidone(3), 1‐(1‐azacyclohept‐1‐en‐2‐yl)‐1‐azacycloheptan‐2‐one(4)and 1‐(phenyliminomethyl)‐2‐pyrrolidone(5), both above the below the melting temperature of the polymer (150‐230°C). Th