Graft copolymerization of acrylic acid onto cocoyam starch by ceric ion in the presence of N,N'-dimethylacetamide

Grafting of acrylic acid onto cocoyam starch, Xanthosoma sagittitolium was initiated by ceric ion--N,N'-dimethylacetamide redox pair in aqueous media. The reaction was characterized by high graft yields of up to 676%, and infrared spectroscopy affirmed the presence of grafted polymer. Graft yield was enhanced by N,N'-dimethylacetamide (DMAc) in the concentration range, 9.0-36.0 x 10⁻⁴M but lower concentrations were more favorable with the ratio of percentage graft, Pg/Pg₀, in the presence and absence of DMAc respectively, of up to 1.34 at 9.0 x 10⁻⁴M of the latter. Ceric ion was nonterminating of the graft reaction and a 10-fold increase in its concentration of 4.16 x 10⁻³M resulted in high efficiency of graft of 50.2% in monomer conversion to grafted polymer. Enhanced homopolymer formation and low efficiency of graft were observed at monomer concentration greater than 0.69M. Long reaction time, greater than 30 min, was unfavorable to the graft reaction and the latter showed negative dependence on temperature in the range, 30-50°C. At 30-min reaction time, the graft yield at 50°C was not more than 70% of the corresponding value at 30°C.