Dielectric characterization of neutralized and nonneutralized chitosan upon drying

Isothermal dielectric loss spectra of neutralized and nonneutralized chitosan were acquired in successive runs from –130°C up to increasing final temperatures, in a frequency range between 20 Hz and 1 MHz. Essentially, three relaxation processes were detected in the temperature range covered: (i) a β‐ wet process, detected when the sample has a higher water content that vanishes after heating to 150°C; (ii) a β process, which is located at temperatures below 0°C, becoming better defined and maintaining its location after annealing at 150°C independently of the protonation state of the amino side group; and (iii) a σ process that deviates to higher temperatures with drying, being more mobile in the nonneutralized form. Moreover, in dried neutralized chitosan, a fourth process was detected in the low frequency side of the secondary β process that diminishes after annealing. Whether this process is a distinct relaxation of the dried polymer or a deviated β‐ wet process due to the loss of water residues achieved by annealing is not straightforward. Only β and σ processes persist after annealing at 150°C. The changes in molecular mobility upon drying of these two relaxation processes were evaluated. © 2005 Wiley Periodicals, Inc. Biopolymers 81: 149–159, 2006 This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com