Complex-radical terpolymerization of styrene, maleic anhydride, and N-vinyl pyrrolidone via γ-ray radiation: Synthesis, characterization, and micellization

Radical terpolymerization of donor-acceptor monomers, i.e. styrene (St), maleic anhydride (MA) and N-vinyl pyrrolidone (NVP) were carried out in methyl ethyl ketone(MEK) under γ-ray radiation at room temperature. Constants of copolymerization, complex formation, and some kinetic parameters for the monomer systems were studied by UV, 1H NMR, Kelen-Tüdöş and Fineman-Ross methods, respectively. Obtained results show that terpolymerization proceeded mainly through 'complex' mechanisms in the state of near-binary copolymerization of St⋯MA and MA⋯NVP complexes. The homo-polymerization of St and NVP and the copolymerization between St and NVP could hardly be occurred. The possible reason is the effect of protection from radiation by styrene with its aryl-ring structure and/or the much larger reactivity of the complex copolymerization between the donor-acceptor monomers. The terpolymer self-assembles into micelles in aqueous solution. Polymeric micelles, composed of chains of St-MA and MA-NVP with equal molar ratio, displayed narrow size distribution of about 120 nm. The critical association concentration of micelles was determined to be around 3 mg/L.