Studies on anionic polymerization of lactams. Part III. Copolymerization of pyrrolidone and caprolactam

On reacting acetylcaprolactam (AcCL) and pyrrolidonate MgBr (Py^?) in tetrahydrofuran solution, transacetylation takes place, giving acetylpyrrolidone (AcPy) and caprolactamate MgBr (CL^?). The rate constants for the transacetylation reactions were measured at 25°C. Their values in units of liters/mole-second were: The rate constants for the addition reactions measured were: As the transacetylation is much faster than the addition reaction the copolymer composition should be given by the equation: where K_trans, the transacetylation equilibrium constant, equals 0.3 while K_acidity reflects the relative acidities of the monomers and its value (from the literature) is about 0.4. Pyrrolidone is, therefore, more reactive than caprolactam in anionic copolymerization by a factor of about 8.