Non‐classical radical propagation

Complexing of acrylic and methacrylic monomers with Lewis acids results both in their resonance stabilization and polarization of C=C bonds which cause a change of their reactivity in a classical sense. However, non‐classical reaction paths including growing radical‐monomer coordination in the transition state apparently play an important role in homo‐ and copolymerization of such monomers. An alternating copolymerization of acrylic and methacrylic monomers with olefines and dienes in the presence of Lewis acids in some cases proceeds due to a “classical” cross propagation rate constant increase. In the other cases alternation is caused by non‐classical mechanisms such as addition of comonomer complexes as the whole and (or) growing radical–monomer precomplexing. An alternating copolymerization of conventional donor‐acceptor monomer pairs also can proceed via classical and non‐classical reaction paths. ESR method combined with using of spin trap and corresponding kinetic measurements can be successfully applied for clarification of a propagation mechanism in each case.