Amylose graft polymers made by 60Co gamma-irradiation†

Model products were needed to elucidate structure-property relationships in a starch graft polymer research program. Simultaneous irradiation of amylose and acrylamide in oxygen-free, dilute aqueous solutions gave graft polymers with maximum add-on of about 16 percent. The graft polymers were separated from homopolymer and subfractionated by incremental additions of nonsolvent (methyl or ethyl alcohol) to irradiated aqueous reaction media. The graft polymers were fairly homogeneous in graft content. Effects were determined of ratios of monomer to substrate, dose rate, and total dose on yield, graft content, intrinsic viscosity, and homopolymer characteristics. Under some conditions, crosslinks probably formed between graft side chains. Large differences in solution properties of a synthetic mixture of separately irradiated amylose and acrylamide and an irradiated solution of amylose and acrylamide indicated that grafting had occurred. Further evidence for true grafting was based on the action of a selective precipitant, n-butyl alcohol, on graft polymer solutions.