Cationic polymerizations of 2‐alkyloxazolines catalyzed by bismuth salts

Acidic bismuth salts, such as BiCl₃, BiBr₃, BiJ₃, and Bi‐triflate catalyzed the ring‐opening polymerization of 2‐methoxazoline (MOZ) in bulk at 100 °C, whereas less acidic salts such as Bi₂O₃ or Bi(III)acetate did not. Bi‐triflate‐catalyzed polymerizations of 2‐ethyloxazoline (EtOZ) were performed with variation of the monomer–catalyst ratio (M/C). It was found that the molecular weights were independent of the M/C ratio. The formation of cationic chain ends and the absence of cycles was proven by reactions of virgin polymerization products with N,N‐dimethyl‐4‐aminopyridine or triphenylphosphine. The resulting polymers having modified cationic chain ends were characterized by ¹H NMR spectroscopy and MALDI‐TOF mass spectrometry. The polymerization mechanism including chain‐transfer reactions is discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4777–4784, 2008