Syntheses and characterisation of graft copolymers of maize starch and methacrylonitrile

Grafting of methacrylonitrile (MAN) onto dried maize starch using eerie ammonium nitrate (CAN) as an initiator has been studied gravimetrically under nitrogen atmosphere in aqueous medium. The percentage grafting is favoured by increasing monomer concentration and reaction time but is affected by higher concentration of initiator and high temperature. No rafting was observed beyond 45 degrees C. The optimum conditions established for grafting were: [CAN] = 0.002 mol/l which was added in molar nitric acid; [MAN] = 0.755 mol/l; reaction time, 180 min; and temperature, 35 degrees C. The graft copolymers were analyzed by infrared spectroscopy and acid hydrolysis. The grafting of methacrylonitrile onto starch does not alter the thermal stability of starch. The crystalline region of starch was also involved in grafting. Scanning electron microscopy showed a thick polymer coating of grafted PMAN on the starch surface. (C) 2000 Elsevier Science Ltd. All rights reserved.