|2. Müller, A.H.E.; Höcker, H.; Schulz, G.V.: Rate Constants of the Tactic Monomer Addition in the Anionic Polymerization of Methyl Methacrylate in THF with Cesium as Counterion, Macromolecules 10, 1086 (1977)|
Tacticity measurements of PMMA samples prepared anionically in THF with Cs+ as counterion show that tactic monomer addition in this system does not obey Bernoullian statistics, the average sequence lengths being shorter than to be expected. It is shown that the Coleman-Fox model is not applicable; the results rather can be fitted by Markovian statistics. In conjunction with the overall rate constant known from kinetic measurements the rate constants for the four different ways of monomer addition are calculated, assuming a first-order Markov process. The Arrhenius plots of these constants show that syndiotactic addition is favored energetically but has to meet higher steric requirements regarding the transition state.