Chitin and chitosan nanofibers with different degrees of deacetylation (DD) were fabricated by electrospinning using 1,1,1,3,3,3-hexafluoro-2-propanol (HELP) as the spinning solvent and by subsequent deacetylation using a 40% aqueous NaOH Solution at 100 degrees 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. (C) 2009 Elsevier Ltd. All rights reserved.