Magnetic resonance and conductivity study of a gelatin-based polymer gel electrolyte

This work reports results from proton nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR) and complex impedance spectroscopy of gelatin-based polymer gel electrolytes containing chloridric acid, cross-linked with formaldehyde and plasticized with glycerol. Ionic conductivity of 4 × 10−5  S/cm were obtained at room temperature for samples prepared with 0.1 M of HCl. Proton (1H) lineshapes and spin-lattice relaxation times were measured as a function of temperature. Activation energies extracted from the 1H NMR relaxation data are in the range of 23–25 kJ/mol. The EPR spectra, which were carried out in samples doped with copper perchlorate, were interpreted with the aid of an axial spin Hamiltonian and indicate the presence of two different Cu2+ species in axially distorted sites. Copper complexation with both hydrogen and nitrogen was verified by electron spin-echo envelope modulation (ESEEM) techniques.