Two epoxy polymers were prepared by curing the diglycidyl ether of bisphenol A (DGEBA) epoxy resin with two hardeners: the ethylenediamine (EDA) and the 3,3'-diaminodiphenyl sulfone (33'DDS) which are respectively aliphatic and aromatic. Structural properties of DGEBA/EDA and DGEBA/33'DDS polymers were investigated by means of grazing incidence X-ray reflectometry. Their dielectric properties were studied using the dielectric relaxation spectroscopy (DRS) over wide ranges of temperature (from -80 to 200 degrees C) and frequency (from 10(-1) -10(6) Hz), and thermally stimulated depolarization current (TSDC) technique. X-ray data revealed the presence of a locally periodic nanostructure in polymer cured with the aromatic hardener (DGEBA/33'DDS). gamma and alpha dipolar relaxations were highlighted for the two polymers while the Maxwell-Wagner-Sillars (MWS) relaxation appears only in the DGEBA/33'DDS. The electric modulus data were fitted using Havriliak-Negami approch. Conductive properties of epoxies were investigated. Ac conductivity data reveal that DGEBA/EDA is more conductive than the DGEBA/33'DDS. (C) 2015 Elsevier Ltd. All rights reserved.