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 degrees 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 degrees 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.
Viciosa
M T
MT
REQUIMTE/CQFB, Departamento de Química, FCT, Universidade Nova de Lisboa, 2829-516 Caparica, Portugal.
Dionísio
M
M
Silva
R M
RM
Reis
R L
RL
Mano
J F
JF
D048271:Chitosan / Q000032:analysis* / Q000737:chemistry*; D004563:Electrochemistry / Q000379:methods; D009038:Motion; D013057:Spectrum Analysis / Q000379:methods; D013818:Thermogravimetry / Q000379:methods
D048271:Chitosan