Polymerization of lactams, 52. Anionic polymerization of 2-pyrrolidone accelerated with CO2, part 1

The polymerization of 2-pyrrolidone ( 1 ) initiated with its potassium salt (2-oxo-1-pyrrolidinylpotassium) ( 2 ) and accelerated by the presence of CO₂, was investigated. For the optimal concentration of 2 (≈5 mol-%) and 0,5 mol-% CO₂, the most suitable polymerization temperature was found to the range between 45 and 55°C. The variation of CO₂ concentration, 0,5 < [CO₂] < 3 mol-%, does not affect the polymerization yield under the optimal conditions. The similarity of the course of polymerization in the presence of CO₂ directly introduced into the reaction mixture with that in the presence of isolated carboxylate of 1 , is considered as a proof that CO₂ is transformed into the active potassium carboxylate of 1 . The order of polymerization reaction with respect to initiator was found to be ≈0,8 indicating the complexity of the reaction mechanism.