Investigation of the end group fidelity at high conversion during nitroxide-mediated acrylate polymerizations

The impact of formation of midchain radicals-and more specifically the follow up reactions of β-scission and macromonomer addition to propagating macroradicals stemming from this process-on the nitroxide-mediated polymerization of acrylates have been studied via kinetic modeling with the software package Predici on the example of butyl acrylate polymerization at 120 °C. Only small influences of the midchain radical formation on the livingness of the process is observed, however, large effects must be envisaged by the (reverse) scission reaction at high monomer-to-polymer conversions. A significant loss of livingness, depending on the temperature, monomer and initiator concentration must be expected at elevated stages of polymerizations. For a polymerization at 120 °C and a target chain length of 100, less than 75% livingness of the polymer product can be expected at 80% conversion. From this point of polymerization on, significant broadening of the overall polymer product is predicted in accordance to literature data and eventually the chain-length-conversion relation is lost at the end of reaction.