Carboxymethylation of Starch and Oxidized Starches

Abstract Research was designed to tailor polymeric materials for specific utilization, namely sizing of cotton textiles by making use of maize starch and rice starch. Hence both starches were subjected independently to oxidation with potassium persulphate to obtain starches with different molecular sizes. The original starches and the oxidized starches were then partially carboxymethylated with monochloroacetic acid under the catalytic influence of sodium hydroxide. In this way the molecular structure of starch, i.e., the molecular weight of the polymeric backbone and substituents present thereon, could be controlled. Results signify the following: (a) persulphate oxidation yields mixed type (acidic/reducing) of oxidized starch since the latter contains both carbonyl and carboxyl groups; (b) the extent of oxidation relies on the severity of the conditions used but it is certain that maize starch is more susceptible towards oxidation than rice starch due mainly to structural differences; (c) oxidation of starch prior to carboxymethylation enhances the amenability of starch to carboxymethylation regardless of the kind of starch used and; (d) when applied as sizing agents, carboxymethyl starches derived from oxidized starches proved to be the best and the original starches the least while oxidized starches stood in mid‐way position.