Radical and spontaneous thermal polymerizations of some captodative‐substituted acrylates

The polymerization of some captodative‐substituted acrylates was examined in the presence and absence of 2,2′‐azoisobutyronitrile (AIBN) at 60 °C. Methyl acrylates, substituted by acetoxy, methoxy and ethylsulfenyl groups in α‐position, and tert‐butyl α‐methoxyacrylate homopolymerized with and without this initiator. The rate of AIBN‐initiated homopolymerization of methyl α‐acetoxyacrylate was as high as that of methyl methacrylate in spite of the captodative‐substituted monomer, and these acrylates also gave polymers spontaneously in remarkably high yield even under conditions under which styrene and methyl methacrylate are not polymerized. Copolymers of these monomers with styrene also were obtained in the presence and in the absence of AIBN. The mechanism of the initiation of the spontaneous thermal polymerization is discussed on the basis of ESR spectra, reaction intermediates and radical inhibition experiments.