Two new families of biodegradable poly[(epsilon-caprolactam)co-(epsilon-caprolactone)] and poly[(epsilon-caprolactam)-co-(delta-valerolactone)] copolymers were synthesized via anionic polymerization. The polymerization was activated with macroactivators (MAs) based on telechelic poly(epsilon-caprolactones) (PCLOs) and poly(delta-valerolactone) (PVLO) polyols. The molecular weights of the polyesters were varied to obtain a large diversity of copolymer structures and properties. The MAs were prepared by reaction of reactive hydroxyl end-groups of PCLO polyols or hydroxyl-carboxyl end-groups PVLO polyol with isophorone diisocyanate (IF). The diisocyanate-end-capped poly(lactones) were additionally blocked in sit a with epsilon-caprolactam to receive corresponding carbamoyllactam derivates. Analyses of the isolated. products by FTIR, H-1 NMR spectroscopy, and size exclusion chromatography indicated that nearly quantitative end-functionalization was achieved in all cases. The prepared MAs reduce the polymerization time to several minutes and improve the toughness of the synthesized poly(esteramides). (C) 2007 Wiley Periodicals, Inc.