Dielectric studies of amylose, amylopectin and amylose–stearic acid complexes

Abstract

The effect of structure creation and moisture content on the dielectric properties of amylose, amylopectin and amylose–stearic acid complexes is presented. Three dielectric features have been identified in these systems. At low temperature, a dipole relaxation process is observed which is assigned to the reorientation of the CH2OH group. At ambient temperatures, a thermally activated relaxation is assigned to liberation–local chain motion. In certain systems at high temperatures, a Maxwell Wagner Sillars process is observed associated with the heterogeneous nature of media and is ascribed to the gel structure in the amylose–stearic acid complex. The low temperature relaxation is sensitive to the moisture content, the water molecules being bound to the CH2OH groups and the activation energy being reduced as the water content is increased. Comparison of the relaxation observed in amylose and amylopectin indicates that chain branching increases the activation energy and inhibits the local reorientation motion of the chain backbone. The relative magnitude of the relaxation processes and their activation energies are discussed in term of the structure of the polymer backbone, the nature of the complex formed with stearic acid and the extent to which order is created by thermal treatment. This paper gives insight into the changes in amylose mobility accompanying the formation of the various complexes.