EPR study of radical trapping of RAFT polymerization of Multifunctional Acrylates

Electron Paramagnetic Resonance (EPR) was used to monitor radical trapping during Reversible Addition-Fragmentation chain Transfer (RAFT) polymerization of acrylate monomers with different degrees of functionality. Monomers used for the study were 1, 6-Hexanidiol \underline {Di}acrylate (HDODA), Trimethylopropane \underline {Tri}acrylate (TMPTA), and Pentaerythritol \underline {Tetra}crylate (PETA). X-band EPR spectra were obtained for approximately 0.2 g of samples in a 4 mm quartz tube heated at 50$^{0 }$C inside the cavity. The trapped radicals' signals were first observed after the samples were heated for 400-500 minutes. Radical density continued to increase for an additional 180 -190 minutes. EPR spectra of RAFT samples of TMPTA and PETA were compared with subsequent spectra produced by traditional free radical polymerization.