Self-regulation of controlled radical polymerization

The number of stable free radicals in solution usually increases in a controlled radical polymerization due to irreversible side reactions of free polymer-radicals. In our approach, this increase is, depending on the amount of side reactions, prevented by slow decomposition of the counter radical and by simultaneous formation of new initiating species. While the controlled radical polymerization in the presence of completely stable radicals is generally possible only (at least without great difficulty) for monomers with the tendency to spontaneous initiation (e.g. thermal initiation of styrene), our system is "self-regulating" and therefore independent of initiating properties of the monomer. The concept was proven by controlled radical polymerization of methacrylates and styrene in the presence of two triazolinyl radicals 1 and 2 with different thermal stabilities.