No Apparent Correlation of kp with Steric Hindrance for Branched Acrylates

The Arrhenius parameters of the propagation rate coefficient, k(p), are determined via the pulsed laser polymerization-size exclusion chromatography (PLP-SEC) method for five branched acrylates (tert -butyl (tBA), isobornyl (iBoA), benzyl (BnA), 2-ethylhexyl (EHA), and 2-propylheptyl acrylate (PHA)) in 1 M solution in butyl acetate (BuAc) to complete the series, published by Haehnel et al. in 2014, of branched acrylates (isononyl (INA-A), tridecyl (TDA-A and TDN-A), heptadecyl (C17A), and henicosyl acrylate (C21A)) in solution that do not show a trend in k(p). Furthermore, the propagation rate coefficients of the branched acrylates in 1 M solution are critically compared with the branched acrylates in bulk as well as branched methacrylates. A summary of the trends and family-type behavior for the linear and branched (meth) acrylates as well as methacrylates with cyclic ester side chains is provided. For the branched acrylates in 1 M solution, no clear trends of the propagation rate coefficients, k(p), or Arrhenius parameters A and E-A are detectable and-in contrast to the corresponding methacrylates-there is no family-type behavior observed in solution as well as in bulk.