Nitroxide-mediated polymerization of methyl methacrylate using an SG1-based alkoxyamine : How the penultimate effect could lead to uncontrolled and unliving polymerization
Résumé
The nitroxide‐mediated polymerization (NMP) of MMA initiated with a new crowded SG1‐based alkoxyamine was performed. Contrary to the results expected after a kinetic analysis (Fischer's diagram), the polymerization of MMA at 45 °C with SG1 showed only partial control and livingness during the first 15% of conversion. Simulations using PREDICI highlighted that the kinetic rate constants currently in use had not been correctly estimated and that a strong penultimate effect drastically increased the equilibrium constant K (7 × 10−7), preventing a well‐controlled polymerization. Experimental determination of the kc value (1.4 × 104 L · mol−1 · s−1) confirmed a strong penultimate effect on the recombination reaction, whereas for the dissociation reaction this effect is lower (kd = 10−2 · s−1).