Propagation Rate Coefficients of Acrylate−Methacrylate Free-Radical Bulk Copolymerizations

Abstract

Copolymerization propagation rate coefficients, kp,copo, have been measured for the binary systems methyl acrylate (MA)−dodecyl methacrylate (DMA), butyl acrylate (BA)−methyl methacrylate (MMA), dodecyl acrylate (DA)−DMA, and DA−MMA at 40 °C and 1000 bar by the pulsed laser polymerization (PLP)−size-exclusion chromatography (SEC) technique. These acrylate−methacrylate systems are interesting because of the significant difference, by more than 1 order of magnitude, between the homopropagation rate coefficients of the two families. Reactivity ratios, ri, are determined from monomer feed compositions and the NMR spectroscopically measured copolymer compositions. The resulting ri values for the four acrylate−methacrylate copolymerizations agree within experimental accuracy. Moreover, these ri data are surprisingly close to reactivity ratio data estimated from individual addition rate coefficients to MA and MMA, respectively, of appropriate small (meth)acrylate-type free radicals. Such addition rate coefficien...