Magnetic resonance and conductivity study of gelatin-based proton conductor polymer electrolytes

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

“…5, at the nitrogen hyperfine frequencies, is an indication of strong electron-nitrogen couplings. This result is very similar to what has been observed before [18] and indicates that both, the 1 H nuclei (of the gelatin and the plasticizer) and the 14 N nuclei (of the glycine and proline groups of the gelatin) are close enough to interact with the copper ion. These two different environments for the copper can explain the observation of two different copper species in the CW-EPR spectrum.…”

“…It is possible to observe that the ionic conductivity increases monotonically with HCl concentration. It should be noted that these conductivity values are higher than those obtained before for the gelatin-based electrolyte prepared with acetic acid [18], but a quantitative comparison among these two systems is difficult to be established because of their different acid concentration: 18 wt% for the latter electrolyte compared to 0.1 M (i.e. 1 wt%) for the former one.…”

“…It should be noted that no apparent difference is observed between the EPR spectra in Fig. 4 and those previously observed for the gelatin-based electrolyte prepared with acetic acid [18], except for the hyperfine lines which are broader for the former electrolyte. The empirical model of Blumberg and Peisach, which correlates the pair (g , A ) of Cu 2+ EPR parameters to the bonding nature of the Cu 2+ in copper complexes [29], suggests that in the gel electrolyte the cooper is coordinated to one nitrogen and three oxygen.…”

“…Proton ( 1 H) nuclear magnetic resonance (NMR) lineshapes and spin-lattice relaxation times measurements were used to characterize the proton mobility and electron paramagnetic resonance (EPR) experiments were carried out in samples doped with copper perchlorate in order to investigate the coordination environment of the cation in the gel electrolyte. The NMR results show that the proton mobility is dependent on acetic acid content in the gel electrolytes and the pulsed EPR electron spin echo envelope modulation (ESEEM) technique identified the involvement of both, hydrogen and nitrogen atoms, in the copper complexation of the gel electrolyte [18].…”

“…This behavior is in contrast with those observed in the gel electrolytes prepared with acetic acid, which displayed an asymmetric shape around the relaxation rate maximum. These asymmetric curves were interpreted by assuming the existence of two distinct proton dynamics, one associated with the protons of the acetic acid and another one caused by protons in different environments [18]. Possibly, the asymmetry of the relaxation curves in Fig.…”