Fe3+ Metal Ion-Doped Ionic and Double Network Hydrogels Based on Sodium Carboxymethyl Cellulose (NaCMC): Broadband Dielectric Spectroscopy Investigations

Ionotropic gelation of polyelectrolyte-based hydrogels is getting more importance due to its wider application possibilities in biomedical, tissue engineering, water treatment, electronic skin and fabrication of multifunctional materials. We synthesized ferric ion (Fe3+)-doped sodium carboxymethyl cellulose (NaCMC) hydrogel films and double network hydrogels (primarily crosslinked via esterification and addition of Fe3+ ion to form secondary crosslinks). Broadband dielectric spectroscopy (BDS) studies are performed using electrochemical impedance spectroscopy results to understand the structure property relation and ion transport in the frequency range of 0.1 Hz- 1 MHz. Dielectric relaxation peak is observed for NaCMC in water with relaxation time of 8.9 x 10(-5) s; however, dielectric relaxation peaks disappeared in ionically crosslinked hydrogels on increasing Fe3+ ion concentration with decrease in dc conductivity (4.60 x 10(-1) S/cm to 6.25 x 10(-2 )S/cm) and also electrode polarization can be due to ion binding, however, some signals of dielectric relaxations are observed for double network hydrogels in derived imaginary part of permittivity with extraordinary high values of dc conductivity (0.46-2.47 S/cm) with Fe3+ addition can be due to release of H+ and Na+ ions.