Pressure dependence of propagation rate coefficients in free-radical homopolymerizations of methyl acrylate and dodecyl acrylate

Propagation rate coefficients (k(p)) for the homopolymerization of methyl acrylate (MA) and dodecyl acrylate (DA) were determined by the pulsed laser polymerization (PLP)/size-exclusion chromatography (SEC) technique at pressures between 100 and 2000 bar. The activation volumes for the propagation step, Delta V-#(k(p)), of MA and DA are identical within experimental accuracy, but are clearly different from the previously reported Delta V-#(k(p)) of methyl and dodecyl methacrylate. For both the alkyl acrylates and methacrylates a pronounced family-type behaviour of k(p) is seen, with k(p) being slightly enhanced toward larger ester size.