Complexation and blending of starch, poly(acrylic acid), and poly(N-vinyl pyrrolidone)

Starch is often modified to improve its end-use properties. In this work, we sought to improve the properties of starch through non-covalent means, viz., the blending of starch with poly(acrylic acid), poly(N-vinyl pyrrolidone), and poly(N-vinyl pyrrolidone)-iodine. An emphasis was placed on the rheological and gel forming properties. Starch was found to form a synergistic mixture with poly(acrylic acid). It has no effect on poly(vinyl pyrrolidone) but produces a gel with poly(vinyl pyrrolidone)-iodine. The addition of a small amount of a third polymer caused either increased viscosity (at low addition levels) or gel formation (at higher levels). Through gel formation, a large quantity of starch can be incorporated in the interpolymer complex. These observations are rationalized on the basis of specific interactions among the polymers. Several specific compositions of these blends may find applications as thickeners and encapsulating agents.