Mechanistic Insight in the Enzymatic Ring-Opening Polymerization of beta-Propiolactam

Here we report the polymerization of beta-propiolactam to poly(beta-alanine) catalyzed by the immobilized Candida antarctica lipase B (N435). The polymer is characterized by (1)H-NMR spectroscopy and MALDI-ToF mass spectrometry. The best results were obtained with N435 (dried for 24 hours in vacua at 46 degrees C) in toluene at 55 degrees C for a period of 96 hours. Polymerization of beta-alanine was not feasible via the N435 catalyst, showing that the beta-propiolactam ring is needed for this reaction. This finding ruled out reaction mechanisms that resembled enzymatic polymerization of epsilon-caprolactone. Instead, a detailed eight-step mechanism was developed by computational simulation that provided an appropriate description of ring-opening polymerization of beta-propiolactam