A series poly(epsilon-caprolactam-co-epsilon-caprolactone) copolymers (PEAs) were investigated regarding the changes in the structure and characteristics in the context of the variation of temperature (in the range 173-373 K) and epsilon-caprolactone content (from 0.0 to 25.0 wt%) in the comonomers mixture. Anionic copolymerization-rotational molding combined technique was used for obtaining of these amide-rich copolymers, semicrystalline and sensitive to the electric stimulus by polar amide groups, and potential degradable by ester units. For dielectric measurements was taken into account also the variation of frequency in the range of 10(0)-10(6) Hz. The modifications observed by fourier transform infrared spectroscopy (FTIR), broad dielectric spectroscopy (BDS), X-ray photoelectron spectroscopy (XPS), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), scanning electron microscopy (SEM) supporting the increase/decrease of the homogeneity in the copolymers structure induced by variation of the chosen parameters. It was observed that the polymers films show Brill transition on heating. An approximately 15.0% ester residues and about 70% amide component from sample PEA20 are distributed in the "near surface" region. At low frequencies (i.e., 1 x 10(0) Hz) the increasing of temperature over 240 K leads to a temperature dependence of epsilon ''. Over 280 K (at high frequency) and 300 K (at low frequency), the alpha relaxation is visible as a broad shoulder for all samples. The results are presented comparatively. POLYM. ENG. SCI., 59:465-477, 2019. (c) 2018 Society of Plastics Engineers