Effect of the degree of deacetylation on the thermal decomposition of chitin and chitosan nanofibers

Chitin and chitosan nanofibers with different degrees of deacetylation (DD) were fabricated by electrospinning using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as the spinning solvent and by subsequent deacetylation using a 40% aqueous NaOH solution at 100 °C for 0–150 min. The thermal decomposition behavior of the chitin and chitosan nanofibers was examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The thermal stability of the chitin/chitosan nanofibers was decreased with increasing the DD and the peak temperature for thermal decomposition on the TGA curves was shifted to a lower temperature. The activation energies for the thermal degradation of the chitin/chitosan nanofibers were calculated from the TGA curves. The two exotherms corresponding to the decomposition of N-acetyl-d-glucosamime and d-glucosamine units in the chitin/chitosan molecular chains were observed on the DSC thermograms. This suggests that the residual N-acetyl groups had a blocky distribution in the molecular chain, possibly due to heterogeneous deacetylation.