The sol-gel method was employed in the synthesis of di-urethane cross-linked poly(epsilon-caprolactone) (d-PCL(530)/siloxane biohybrid ormolytes incorporating copper perchlorate (Cu(ClO4)(2)). The highest ionic conductivity of the d-PCL(530)/siloxane(n)Cu(ClO4)(2) system is that with n = 10 (1.4 x 10(-7) and 1.4 x 10(-5) S cm(-1), at 25 and 100 degrees C, respectively). In an attempt to understand the ionic conductivity/ ionic association relationship, we decided to inspect the chemical environment experienced by the Cu2+ ions in the d-PCL(530)/siloxane medium. The observed EPR spectra are typical of isolated monomeric Cu2+ ions in axially distorted sites. The molecular orbital coefficients obtained from the EPR spin Hamiltonian parameters and the optical absorption band suggests that bonding between the Cu2+ and its ligand in the ormolytes are moderately ionic. Investigation by photoluminescence spectroscopy did not evidence or allow selective excitation of transitions corresponding to complexed Cu2+ species. (C) 2015 Elsevier Ltd. All rights reserved.