Nitroxide-mediated polymerization of methyl methacrylate using an SG1-based alkoxyamine: How the penultimate effect could lead to uncontrolled and unliving polymerization

The nitroxide-mediated polymerization (NMP) of MMA initiated with a new crowded SGI-based alkoxyamine was performed. Contrary to the results expected after a kinetic analysis (Fischer's diagram), the polymerization of MMA at 45 degrees 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 x 10(-7)), preventing a well-controlled polymerization. Experimental determination of the k(c) value (1.4 x 10(4) L . mol(-1) . s(-1)) confirmed a strong penultimate mate effect on the recombination reaction, whereas for the dissociation reaction this effect is lower (k(d) = 10(-2) . s(-1)).