Contributions to the molecular origin of the dielectric relaxation processes in polysaccharides – the high temperature range

Abstract

Abstract For ionic conducting glasses a concept of correlation of electrical conductivity with dielectric relaxation was developed, which was essential for understanding the relaxation processes found for this substance class. This paper describes on attempt to extend the concept for interpreting the so-called σ-relaxation found in all systems of well dried polysaccharides in the solid state at high temperatures. For various cellulose-based materials, starches and other pure polysaccharides it was found that the activation energies of the dc-conductivity and the dielectric σ-relaxations were well correlated and their values were nearly equal (95–110 kJ/mol) for all substances. The shape and the intensity of this relaxation were nearly independent of temperature for one substance. In cellulose derivatives this process can be only observed, if these have sufficient unsubstituted hydroxyl groups. Highly or persubstituted celluloses show no separable σ-relaxation. Two models are discussed for the interpretation of this relaxation process: the first one assumes a local diffusion process of hydrogen ions between high potential barriers in these disordered systems and the second one a conducting pathway through a badly conducting environment in the material.