Cobalt‐catalyzed alternating and nonalternating copolymerization of carbon monoxide with aziridine

Catalysts CH₃COCo(CO)₃PPh₃ ( 1 ) and HCo(CO)₃PPh₃ ( 2 ) catalyze the copolymerization of aziridine and carbon monoxide. Catalyst 2 can be conveniently generated in situ via reaction of Na⁺Co(CO)₄, N,N‐dimethylanilinium chloride, and PPh₃. The copolymerization alternates at high catalyst loadings to produce poly(β‐alanine). The end groups of the poly(β‐alanine) product are characterized by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry and by comparison of the ¹H NMR spectra of the polymer and a stepwise synthesized model compound. At low catalyst loadings, the polymer product contains both the β‐alanine units and amine units because of nonalternating enchainment of the comonomers. The characterization of the amine units is again supported by comparison of the ¹H NMR spectra of the polymers and the stepwise synthesized model compounds. The molecular weights of the polymers are determined by gel permeation chromatography. The thermal stability of the polymers is probed by differential scanning calorimetry and thermogravimetric analysis. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 376–385, 2003