Scanning Electron Microscopy of Saponified Starch‐g‐Polyacrylonitrile

A series of starch‐g‐polyacrylonitrile (PAN) copolymers was prepared by ceric ammonium nitrate initiation, the only differences being in the degree of swelling and gelatinization of starch granules. This variable was governed by the temperature at which starch‐water slurries were heated before graft polymerization. Graft copolymers were then saponified with sodium hydroxide to convert the nitrile substituents of PAN to sodium carboxylate and carboxamide. Comparison of scanning electron micrographs of each starch‐g‐PAN copolymer with those of the corresponding saponified product showed particles which retain the outward appearance of graft polymerized starch granules. Since starch is soluble in alkali and PAN is also rendered soluble on alkaline saponification, a crosslinking reaction either during graft polymerization or during base saponification is proposed to account for the observation that granules are not totally disrupted or dissolved.