Graft copolymerization onto starch. III. Grafting of acrylonitrile to gelatinized potato starch by manganic pyrophosphate initiation

Abstract Recent development of synthesis and applications in grafting of acrylonitrile (AN) to gelatinized starch by Ce 4+ initiation have been briefly reviewed. Using the Mn 3+ method, the effects of starch pretreatment temperature on grafting parameters in grafting of AN onto starch have been studied. Total conversion of AN to PAN and % add‐on were almost constant and showed only slight variation with increasing starch pretreatment temperature. Average molecular weight of grafts showed, however, an increase by a factor of nearly 10 (i.e., from 0.4 X 10 5 to 4 X 10 5 ) after swelling and gelatinization of the starch, and the grafting frequency (anhydroglucose units per grafted chain) increased in proportion. In grafting of AN onto gelatinized starch, increasing Mn 3+ concentration increased the conversion of monomer and % add‐on, whereas the average molecular weight of grafts and the grafting frequency (AGU/chain) decreased. An increase in the amount of starch also increased the conversion of monomer and the grafting frequency (AGU/chain) but decreased the % add‐on and the average molecular weight of the grafts. Selective solution of PAN homopolymer by dimethylformamide indicated that grafting efficiencies were high in all cases. The results are interpreted in terms of slow termination rates due to high viscosity of gelatinized starch.