Free Radical Initiation Mechanisms in the Polymerization of Methyl Methacrylate and Styrene with 1,1,3,3-Tetramethylbutyl Peroxypivalate: Addition of Neopentyl Radicals
| Autor: | W. Ken Busfield, Ezio Rizzardo, Ian D. Jenkins, Shuji Suyama, Tomoyuki Nakamura, San H. Thang |
|---|---|
| Rok vydání: | 1997 |
| Předmět: | |
| Zdroj: | Journal of the American Chemical Society. 119:10987-10991 |
| ISSN: | 1520-5126 0002-7863 |
| Popis: | The reactions of 1,1,3,3-tetramethylbutyl (tert-octyl) peroxypivalate (1) with methyl methacrylate (MMA) and styrene in the presence of the free radical scavenger 1,1,3,3-tetramethyl-2,3-dihydro-1H-isoindol-2-yloxyl (2) have been studied at 60 °C. tert-Butyl and tert-octyloxyl radicals (3) were generated from the thermolysis of 1. The predominant unimolecular reactions of 3, that is, β-scission to form neopentyl radicals (14b) and a 1,5-H shift to form 4-hydroxy-2,2,4-trimethylpentyl radicals (14c), were observed in both monomer systems. The resulting alkyl radicals underwent selective addition to the two monomers. The relative reactivities of the alkyl radicals toward addition to the monomers were obtained from competitive addition/trapping reactions. The absolute rate constants for the addition of alkyl radicals 14b and 14c to the two monomers at 60 °C were estimated to be 9.5 × 105 and 2.6 × 105 M-1 s-1 to MMA and 4.5 × 105 and 0.7 × 105 M-1 s-1 to styrene, respectively. The low reactivities of 3 and 1... |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|