Electron spin resonance studies of propagating radicals in polymerization. II. Acrylate propagating radicals

Abstract

AbstractFerric chloride‐photosensitized free‐radical initiation was used to generate propagating radicals in polymerization of acrylic acid (AA), methyl acrylate (MA), ethyl acrylate (EA), butyl acrylate (BA), acrylamide (A), and diacetone acrylamide (DAA) in rigid glasses of methanol, ethanol, n‐propanol, isopropanol, or acetone at near liquid nitrogen temperatures. When the temperatures of the glasses were increased, primary radicals derived from the solvents reacted with the monomers to yield propagating radicals. Formation and conformational changes of the propagating radicals at different temperatures were studied by electron spin resonance (ESR) spectroscopy. It was concluded that one type of propagating radical was formed in all cases. However, when the temperature of the rigid glass was increased, the structural conformation of the radical that initially allowed the near‐equivalent interaction of the α‐hydrogen and one of the β‐hydrogens with the unpaired electron generated a three‐line spectrum.