Grafting of methyl methacrylate onto sodium alginate initiated by potassium ditelluratoargentate(III)

Sodium alginate (SA) was graft-copolymerized with methyl methacrylate in an alkali aqueous solution with potassium ditelluratoargentate(III) (DTA) as the initiator. Graft copolymers with both a high grafting efficiency (>90%) and a high percentage of grafting were obtained, which indicated that the DTA-SA redox pair was an efficient initiator for this grafting. The grafting parameters, including total conversion, grafting efficiency, and percentage grafting, were evaluated comparatively. The dependence of these parameters on temperature and time, monomer concentration, initiator concentration, and SA backbone concentration was also investigated. The overall activation energy of this grafting was calculated as 37.50 kJ/mol. Proof of grafting was obtained from gravimetric analysis and IR spectra. A tentative mechanism involving a two-step, singleelectron-transfer process of DTA is proposed to explain the generation of radicals and the initiation of grafting. Some basic properties of the grafted copolymer were studied by instrumental analyses, including thermogravimetry, X-ray diffraction, and scanning electron microscopy.