P. Gurr, M. F. Mills, G. Qiao
Mar 10, 2005
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0
Influential Citations
19
Citations
Journal
Polymer
Abstract
Abstract The low efficiency of p -toluenesulfonyl chloride (TsCl) initiator for the polymerization of methyl methacrylate (MMA), when used in conjunction with N , N , N ′, N ″, N ″-pentamethyldiethylenetriamine (PMDETA) and CuBr under atom transfer radical polymerization (ATRP) conditions was investigated. A major by-product in the formation of poly(methyl methacrylate) was identified as N , N -dimethyl- p -toluenesulfonamide ( 5 ) and accounted for approximately half of the initiator. Compound 5 was shown to form by the direct reaction of PMDETA and TsCl. In a model experiment equimolar amounts of TsCl, PMDETA and CuBr reacted at 80°C in p -xylene resulted in the formation of 5 and two other unsaturated sulfones 2-methyl-3-[(4-methylphenyl)sulfonyl]-2-propenoic acid methyl ester ( 6 ) and 2-[[4-methylphenyl)sulfonyl]methyl]-2-propenoic acid methyl ester ( 7 ), formed by the dehydrohalogenation and subsequent isomerization of an intermediate chloro-adduct, 1-(4-methylbenzenesulfonyl)-2-chloro-2-(methyl)methyl propionate ( 2 ). Molecular modeling predicted the unsaturated sulfone 7 was thermodynamically more stable than the higher conjugated sulfone 6 and this was confirmed by the isomerization of 6 to 7 at room temperature under mild basic conditions. The absence of 6 and 7 in the polymerization of MMA under ATRP conditions showed that in the early stages of polymerization in the presence of excess MMA, the intermediate chloro-adduct 2 is not formed.