Molecular motions in chitosan studied by dielectric Relaxation spectroscopy

Neutralized and nonneutralized chitosan films subject to different thermal treatments were studied by dielectric relaxation spectroscopy from -130 to +150 °C in the frequency range between 20 Hz and 1 MHz. Two main relaxation processes, both arrhenian type, were detected: process I at temperatures below 0 °C with a mean activation energy of 49 ( 1 kJ mol-1, which has the characteristics of a secondary relaxation process related with local chain dynamics, and process II observable at higher temperatures with an activation energy of 94 ( 2 kJ mol-1, correlated with dc conductivity, which is found in dried polysaccharides systems. Process I is always observed in neutralized chitosan, but it is strongly depleted in the wet nonneutralized form. Although the location of process I is independent of NH2/NH3 + side group, process II deviates to higher temperatures with dryness in both chitosan forms, being located at lower temperatures in nonneutralized chitosan.FCT, Foundation for Science and Technology, through the POCTI (POCTI/CTM/47363/2002) and FEDER programs