Low-temperature controlled free-radical polymerization of vinyl monomers in the presence of a novel cyclic dixanthate under γ-ray irradiation
Abstract
The free-radical polymerization of methyl acrylate (MA) has been studied in the presence of a novel cyclic dixanthate under γ-ray irradiation (80 Gy min−1) at room temperature (∼28 °C), −30 °C, and −76 °C respectively. The resultant polymers have controlled molecular weights and relatively narrow molecular weight distributions, especially at low temperatures (i.e., −30 and −76 °C). The polymerization control may be associated with the temperature: the lower the temperature is, the more control there is. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of poly(methyl acrylate) (PMA) samples shows that there are at least three distributions: [3-(MA)n-H]+ cyclic polymers, [3-(MA)n-THF-H]+, and [3-(MA)n-(THF)2-H]+ linear PMAs. The relative content of the cyclic polymers markedly increases at a lower temperature, and this may be related to the reduced diffusion rate and the suppressed chain-transfer reaction at the low temperature. It is evidenced that the good control of the polymerization at the low temperature may be associated with the suppressed chain-transfer reaction, unlike reversible addition–fragmentation chain transfer polymerization. In addition, styrene bulk polymerizations have been performed, and gel permeation chromatography traces show that there is only one cyclic dixanthate moiety in the polymer chain. This article is the first to report the influence of a low temperature on controlled free-radical polymerizations. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2847–2854, 2007
