Graft copolymerization of methyl methacrylate onto silk sericin initiated by ceric ammonium nitrate

A novel redox system, ceric ammonium nitrate (CAN)-silk sericin ( SS) was applied to initiate graft copolymerization of methyl methacrylate (MMA) onto silk sericin in an acidic aqueous solution medium. The effects of monomer concentration, initiator concentration, reaction temperature, and time on grafting parameters had been investigated in detail. The results showed that the graft copolymerization occurred even at as a low temperature as 35 degrees C, and high grafting efficiency and grafting percentage could be achieved at the same time. Taking grafting percentage and grafting efficiency as functions, the optimum reaction conditions were obtained as follows: [SS] = 10g L-1, [MMA] = 0.3 mol L-1, [CAN] = 5.7 x 10(-3) mol L-1, temperature = 35 degrees C, time = 60 min. The structure and morphology of SS and SS-g-PMMA were characterized by fourier transform infrared (FT-IR), H-1-nuclear magnetic resonance (H-1-NMR), scanning electron microscope (SEM) and gel permeation chromatography (GPC). A possible mechanism was proposed to explain the formation of radicals and the initiation.