Polymerization inhibition mechanism of 1,4-naphthoquinone by experimentation and DFT calculations

When the radical polymerization inhibitor 1,4-naphthoquinone (NQ) acts on styrene, the radical capture reaction greatly contributes carbon atoms. In this study, the 1-phenethyl radical, which is a model for the growth radicals of polystyrene, was reacted with NQ using four radical sources, and we identified the reaction product. We confirmed that the same compound was formed upon addition of a small amount of NQ to heated styrene. The frontier orbital energy levels and reaction path energy diagrams were calculated using density functional theory with Gaussian 09, which provided numerical values to support our experimental results.