Photopolymerization of Methyl Methacrylate Initiated by Iodine—Monoethanolamine

Abstract

The photopolymerization of methyl methacrylate (MMA) in the presence of iodine (I2) and monoethanolamine (MEA) was investigated and compared with that of MMA photosensitized by I2—triethylamine. The kinetic data suggested that the photopolymerization of MMA with I2—MEA proceeded by a radical mechanism. The composition curve of the photosensitized copolymerization of MMA and styrene with I2—MEA also supported the radical mechanism.The ultraviolet spectrum of I2 and MEA in dichloromethane solution showed a charge-transfer absorption band at 245 nm, and the absorbance near the maximum wavelength measured by the continuous variation method suggested the formation of a charge-transfer complex with a 1:1 molar ratio of I2 and MEA.It seems likely that monoethanolamine hydroiodide and N-β-hydroxyethylidenemonoethanolamine hydroiodide are formed by decomposition of the charge-transfer complex, and that photolysis of the latter yields a radical of diethanolamine which initiates the polymerization of MMA. Monoethanolamine hydroiodide was also found to have a photosensitizing effect for the polymerization of MMA in an excess of monoethanolamine.