FTIR studies of plasticized poly(vinyl alcohol)–chitosan blend doped with NH4NO3 polymer electrolyte membrane

Fourier transform infrared (FTIR) spectroscopy studies of poly(vinyl alcohol) (PVA), and chitosan polymer blend doped with ammonium nitrate (NH4NO3) salt and plasticized with ethylene carbonate (EC) have been performed with emphasis on the shift of the carboxamide, amine and hydroxyl bands. 1% acetic acid solution was used as the solvent. It is observed from the chitosan film spectrum that evidence of polymer–solvent interaction can be observed from the shifting of the carboxamide band at 1660 cm−1 and the amine band at 1591 cm−1 to 1650 and 1557 cm−1 respectively and the shift of the hydroxyl band from 3377 to 3354 cm−1. The hydroxyl band in the spectrum of PVA powder is observed at 3354 cm−1 and is observed at 3343 cm−1 in the spectrum of the PVA film. On addition of NH4NO3 up to 30 wt.%, the carboxamide, amine and hydroxyl bands shifted from 1650, 1557 and 3354 cm−1 to 1642, 1541 and 3348 cm−1 indicating that the chitosan has complexed with the salt. In the PVA–NH4NO3 spectrum, the hydroxyl band has shifted from 3343 to 3272 cm−1 on addition of salt from 10 to 30 wt.%. EC acts as a plasticizing agent since there is no shift in the bands as observed in the spectrum of PVA–chitosan–EC films. The mechanism of ion migration is proposed for the plasticized and unplasticized PVA–chitosan–NH4NO3 systems. In the spectrum of PVA–chitosan–NH4NO3–EC complex, the doublet CO stretching in EC is observed in the vicinity 1800 and 1700. This indicates that there is some interaction between the salt and EC.

Figure optionsDownload as PowerPoint slideResearch highlights▶ Complexation at hydroxyl region was observed. ▶ NO3− ions did not complex with the polymer host in this work since the vs(NO3−) band did not shift. ▶ Ion conductivity mechanism for PVA-chitosan-NH4NO3 and PVA-chitosan-NH4NO3-EC systems is proposed.