Comparison between thermal sampling and numerical analysis of thermally stimulated depolarization current peaks

Thermal sampling peaks recorded after windowing polarization are studied fo r the segmental mode in poly(epsilon -caprolactone). Also, numerical decomp ositions of the global thermally stimulated depolarization current peak int o pure Debye contributions are performed with direct signal analysis (DSA) and simulated annealing direct signal analysis procedures for Arrhenius and Vogel-Tammann-Fulcher (VTF) temperature dependences, respectively. It is f ound that the results between the experimental and the numerical procedures agree very well and the approximations made in the analysis of the experim ental curves are thus validated, despite the unphysical values for the rela xation parameters found by both methods when using Arrhenius relaxation tim es. On the contrary, when VTF relaxation times are used for the numerical d ecomposition, agreement is found with the results of isothermal dielectric absorption as a function of frequency, together with reasonable values for reorientation energies, pre-exponential factors and VTF temperature. Therma l sampling and DSA also compare well when studying the departure from the z ero-entropy line which indicates the onset of a cooperative character in th e dynamics of molecular motion. Compensation is found whenever the primary relaxation is analyzed with Arrhenius or Eyring relaxation times and does n ot appear when VTF relaxation times are used in the numerical decomposition . (C) 2001 American Institute of Physics.