Specific interaction of starch and polyvinyl alcohols having long alkyl groups

Properties of aqueous solutions of blends of starch and polyvinyl alcohols (PVAs), having alkyl groups as side chains, or at one polymer chain end, were studied in terms of viscosity stability, and transparency. In the case of corn starch, PVAs having butyl, octyl, and dodecyl end groups, as well as PVA copolymers containing small amounts of vinyl versatate, together with itaconic acid, increased the stability of the blended solution. The aqueous solutions of PVA, having dodecyl end groups and oxidized starch blend, also showed good stability in viscosities and considerable increase in transparency, whereas conventional PVA and oxidized starch blend gave turbid aqueous solutions, followed by phase separation. The phenomena were assumed to arise from the interaction of the alkyl group in PVA with starch, forming a helical structure with the alkyl group in the hydrophobic internal part.