Kinetic Study of Radical Homopolymerization of Captodative Substituted Methyl .alpha.-(Acyloxy)acrylates

Abstract

Radical homopolymerizations of some captodative substituted methyl α-(acyloxy)acrylates are studied kinetically by using azo initiators at 30-60 °C. Polymerization rate and the properties of the polymer obtained are much influenced by the acyloxy substituents. Methyl α-acetoxyacrylate (MAA), which was already found to give a polymer with excellent optical properties, shows the highest reactivity and gives a high molecular weight polymer with very poor solubility. Kinetic study shows that the propagation rate constant (k p ) of the polymerization of MAA is larger than that of methyl α-(butyryloxy)-acrylate (MBA) at every temperature, k p = 255 and 114 L/mol.s at 50 °C for the polymerization of MAA and MBA, respectively. The activation energy of the overall polymerization of MAA is estimated to be E a = 16.0 kcal/mol, smaller than that of MBA (E a = 17.4 kcal/mol), although the energies of propagation and termination of MAA are larger than those of the bulky-substituted MBA. The mechanism of the unique polymerization of MAA is discussed based on the kinetic study, ESR spectroscopy, and the physical property measurements of the polymer obtained.