Chemical interaction and conductivity of carboxymethyl κ-carrageenan based green polymer electrolyte

The potential of κ-carrageenan derivatives as a green polymer electrolyte has been explored. κ-Carrageenan extracted from marine red algae was reacted with monochloacetic acid to form carboxymethyl κ-carrageenan. The powders were characterized by reflection fourier transform infrared (ATR-FTIR) spectroscopy,13C nuclear magnetic resonance, 1H nuclear magnetic resonance, X-ray diffraction and elemental analysis to confirm the structural, crystallinity and the degrees of substitution. A green polymer electrolyte of κ-carrageenan and carboxymethyl κ-carrageenan were prepared by solution-casting technique. The films were characterized by reflection fourier transform infrared (ATR-FTIR) spectroscopy and electrochemical impedance spectroscopy to determine the chemical interaction and ionic conductivity. The decrease in intensity of hydroxyl, carbonyl, sulfate and ether band confirmed the polymer solvent complex formation. XRD spectra show that chemical modification of κ-carrageenan does not change its amorphous properties. The ionic conductivity was found to increase by three magnitudes higher with the chemical modification of κ-carrageenan. The conductivity achieved was 2.0 × 10− 4 S cm− 1 for carboxymethyl κ-carrageenan in comparison to 5.3 × 10− 7 S cm− 1 for κ-carrageenan.

► Polymer electrolyte of κ-carrageenan and carboxymethyl κ-carrageenan were prepared.
► Chemical modification on κ-carrageenan did not change its amorphous properties.
► Wavenumber of carbonyl, hydroxyl, sulfate and ether band was shifted.
► Conductivity of carboxymethyl κ-carrageenan improved compared to κ-carrageenan.