AbstractThe formation of paramagnetic intermediates following the irradiation of styrene, α‐methylstyrene, and their mixtures at −90°C in the presence of TiCl4and SnCl4in the polycrystalline heptane matrix was investigated. The effect of light on vinyl aromatic monomers leads to the formation of radical cations of styrene and α‐methylstyrene, which subsequently initiate the polymerization. The polymerization of styrene and α‐methylstyrene supposedly proceeds via the cationi