Controlled radical polymerization of alkyl methacrylates in the presence of NO/NO2 mixtures

Radical polymerization of alkyl methacrylates initiated by AIBN is controlled when conducted in the presence of a mixture of NO/NO2. Reaction of alkyl methacrylates with NO/NO2 leads indeed to the monomer adduct and parent anitro, omega-nitroso oligomers, which are precursors of nitroxides, known to control the radical polymerization of alkyl methacrylates, according to a "Nitroxide-Mediated Polymerization" (NMP) mechanism. Although some side reactions may occur with time (increasing polydispersity), polymerization of MMA initiated by AIBN at low temperature (60 degreesC) after bubbling of NO/NO2 is relatively fast, and the molecular weight is dictated by the amount of NO/NO2. Finally, for the first time, copolymerization of MMA with HEMA (10/1; v/v) has been controlled by this mixture of NO and NO2 although the reaction remains very fast (ca. 65% monomer conversion after 5 h at 60 degreesC), which is of prime importance for coating applications.