First identification of biradicals during thermal [2π + 2π] cyclopolymerization of trifluorovinyl aromatic ethers

The thermal cyclopolymerization of three trifluorovinyl aromatic ether monomers 1,1,1‐tris (4‐trifluorovinyloxyphenyl)ethane (1), 4,4′‐bis(4‐trifluorovinyloxy)biphenyl (2) and 2,2‐bis(4‐trifluorovinyloxy‐ phenyl)‐1,1,1,3,3,3‐hexafluoropropane (3) were monitored in situ using time‐resolved electron paramagnetic resonance spectroscopy over a temperature range of 150–210 °C. The signals observed during the early stages of perfluorocyclobutyl polymer production suggest the formation of a triplet state corresponding to the proposed biradical intermediate with a strong dipole–dipole interaction. A doublet splitting shows the presence of hyperfine coupling due to fluorine. The characterization of radical species formed during the polymerization of monomer 1 using model compounds and polymerization kinetics of monomer 2 are also presented. Copyright © 2007 Society of Chemical Industry