Thermal and Dielectric Properties of Novel Chitosan-Derived Polymers

Abstract

E)−3-benzyleidene amino chitosan (CHI-ph) and 2,4-dihydroxy-E)−3-benzyleidene amino chitosan (CHI-OHph) were synthetized by the reaction of chitosan with benzaldehyde and 2,4-dihydroxy–benzaldehyde, respectively. The chemical structures of the formed polymers were characterized by FTIR and microanalysis. FTIR confirmed the chemical structure of the new polymers (CHI-ph and CHI-OHph). The x-ray diffraction measurements confirmed the amorphous nature of chitosan and its derived polymers. The thermal stability of chitosan and its derived polymers were investigated using TGA and DSC measurements. TGA analysis showed that polymers are stable from room temperature up to 373 K. The dielectric constants and AC conduction mechanism of chitosan, CHI-ph and CHI-OHph were investigated in the frequency range 100 Hz–5 MHz, and temperature range 305–395 K, in bulk form. In general, real and imaginary parts of the dielectric constant are found to decrease with increasing frequency. Also, the ac conductivity increases with increasing frequency for the three polymers. The conduction mechanism was investigated and was found to obey correlated barrier hopping with maximum barrier heights of 0.212, 0.313 and 0.254 eV for chitosan, CHI-ph and CHI-OHph.