On the Nature of the Interaction between Starch and Iodine

Abstract

(1) It is postulated that the interaction between starch and iodine in the amylose‐iodine complex is of dipolar nature. (2) A model for such dipolar interaction is proposed and the necessity for a cooperative effect is discussed. (3) The interaction energy is calculated as a function of a parameter x and it is shown that this parameter possesses a critical value at which a ``condensation'' of iodine into the complex occurs. (4) It is demonstrated that it is physically reasonable for this parameter to attain its critical value. (5) It is shown that additional stabilization may occur as a result of the formation of a resonating ``polyiodine'' chain at high dipolar interaction having a I–I distance and heat of formation which compares favorably with experiment. (6) Application of the theory is made in discussing the stability of the polyvinyl alcohol‐iodine complex. (7) The color of these complexes is discussed in terms of the theory.