Rapid Analysis of Starch Graft Copolymers

Starch graft copolymers are expected to become increasingly important as industrial and consumer chemicals in a large variety of end uses. Therefore, a quick and accurate analytical characterization of the graft copolymer is desirable. Vinyl side chains from starch-vinyl graft copolymers have preViously been isolated by several methods. Brockway (1) hydrolyzed the starch moiety with 1 N HCl at reflux temperature for 4-6 hr and recovered the vinyl side chains; such vigorous treatment, however, can alter sensitive functional groups of many vinyl polymers. Fanta et al. (2) treated starch-vinyl graft copolymers with ex-amylase at 50°C for 5 hr to hydrolyze the starch moiety, but hydrolysis was often incomplete in highly grafted copolymers. More recently, Gugliemelli et al. (3-5) have shown that periodate-oxidized starch depolymerizes in anhydrous methyl alcohol at room temperature with catalytic amounts of sodium methoxide to yield water-soluble compounds. This reaction sequence was used to remove the starch moiety from a number of starch graft copolymers. Since the reported procedures for analyzing starch graft copolymers are time-eonsuming or give incomplete results, we investigated a new method for decomposition and removal of the starch moiety in starch·vinyl graft copolymers based on the rapid oxidation of starch with perchloric acid in a glacial acetic acid medium.