Dielectric Relaxations in Chitin Evidence for a Glass Transition

7 DIELECTRIC RELAXATIONS IN CHITIN EVIDENCE FOR A GLASS TRANSITION 

These films are cooled under vacuum from 120 °C to room temperature (20 °C) and then a second measurement is performed in the dry annealed films. To calculate water content on these films, TGA measurements were performed in dry samples (heated at 120 °C in oven overnight). After 1 h at 120 °C (dry annealed films), no further change in weight is observed the films were cooled to 20 °C and reheated. The second TGA scan for dry annealed chitin films shows free water content of circa 0.1% (dash-dotted line. Fig. 2.5). Using the same annealing methodology in the dielectric and TGA measurements, we can monitor the water content in the samples. 

Modulated DSC thermograms (Fig. 2.7) for chitin films after water removal were scanned a second time from 20 to 250 °C. The objective was to see whether a glass transition would manifest. However, as stated in Section 2.1, controversy centers on whether a glass transition can be detected. In our case, there is no clear evidence of the glass transition hence, it is not possible to draw any conclusion from the thermal analysis. As explained earlier, some authors assign no for chitin [11], while others 

Crystal structure analysis was performed using a 2100-Rigaku diffractometer equipped with the CuK a radiation (A, = 1.5406 A) in the 26 range from 5° to 55°, at 30 and 120 °C and operating at 30 kV and 16 mA. 

Wet chitin Dry annealed chitin (100 °C overnight heat treatment) Dry annealed t=30 min Dry annealed t=45 min Dry annealed t=60 min 

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