Radical Chemistry of Tetrazenes: Access to Polymers with Pristine Tetrazenyl Chain Ends and Depolymerization Applications

We report the first radical reaction of tetrazenes- i.e., functions with four consecutive nitrogen atoms with a linear N-N═N-N chain-that retains the characteristic 4N pattern. Selective hydrogen atom transfer (HAT) in the α-position of the 4N chain enables the free radical polymerization of various polar and nonpolar monomers. The tetrazene units play a dual role. Its decomposition generates aminyl radicals that can undergo HAT with another tetrazene molecule and lead to initiating C-centered radicals. Contrary to what was previously thought the aminyl radicals never add to the monomers. The polymers obtained feature tetrazene chain ends, which can be harnessed as macro-initiators to further grow the polymer chains. Heating of the former above the ceiling temperature leads to cleavage of the tetrazene function, which enables depolymerization by unzipping of polymethyl methacrylate (PMMA) and polystyrene (PS).