Synthesis and characterization of multi-active site grafting starch copolymer initiated by KMnO4 and HIO4/H2SO4 systems.

A novel initiator system containing KMO4, HIO4, and H2SO4 for synthesizing grafting starch copolymers is reported. In this system, KMnO4 was used to oxidize the primary hydroxyl group to aldehyde group of glucose in the starch, and the formed aldehyde group reacted with Mn(4+), Mn(3+) to afford starch free radical. At the same time HIO4 perform as the oxidant to open the C2C3 bond of glucose ring in starch to form two more aldehyde groups, and then two more free radicals are generated. As a result one glucose unit could provide ultimately three active sites for starch grafting reaction. Graft copolymers with a higher grafting ratio and grafting efficiency could be obtained by using the composite initiation system than the KMnO4/H2SO4 initiation system. The grafting of polyacrylamide onto the corn starch backbone was confirmed by viscometry, elemental analysis, infrared spectroscopy, nuclear magnetic resonance, X-ray diffraction and scanning electron microscopy.