This book focuses on the characterization of the amorphous phase of polymers, whether they are pure amorphous or semi-crystalline ones, above Tg or below Tg, by studying the relaxation of dipoles and space charges naturally found in their structure after they have been activated by the application of a voltage field. The experimental deconvolution of the relaxation modes responsible for internal motion in the amorphous phase is coupled with a mathematical procedure (Thermal-Windowing Deconvolution-TWD) that leads to the understanding of their coupling characteristics which, it is shown, relate to the state of the material itself, for instance its non-equilibrium state or its internal stress for matter belonging to interfaces between aggregated or dispersed phases. Describes quantitatively the Thermal Stimulated Depolarization techniques of polymer characterization (TSD, TWD), i.e. how to decouple the relaxation modes collectively interacting (interactive coupling) and relate it to the thermodynamic properties of the amorphous phase. Understands the results of depolarization in terms of the new physics of polymer interactions: the Dual-Phase model, here applied to the dipoles-space charge dynamics. Provides a roaster of CASE STUDIES: practical applications of the TSD and TWD characterization techniques to describe coupled molecular motions in resins, medical tissues, wood, blends and block copolymers interfaces, rubbers, can coatings, internal stress in molded parts, etc