Individual chitin nano-whiskers prepared from partially deacetylated α-chitin by fibril surface cationization

alpha-Chitin was partially deacetylated to degrees of N-acetylation (DNAc) 0.74- 0.70 by 33% NaOH treatment at 90 degrees C for 2-4 h. Solid recovery ratios or yields of the products were 85-90%. Crystallinity index and crystal size of the original alpha-chitin were maintained, showing that the partial deacetylation mostly occurred on the alpha-chitin crystallite surfaces. Transparent and highly viscous liquids were obtained by disintegration of the partially deacetylated chitins in water at PH 3-4. Transmission electron microscopy (TEM) revealed that the liquids consisted mostly of individual nano-whiskers with average width and length 6.2 +/- 1.1 and 250 +/- 140 nm, respectively. Some alpha-chitin nano-fibrils of more than 500 nm in length were also detected in TEM images. Because the DNAc values 0.74-0.70 correspond to 1.34-1.56 mmol g(-1) C2-amino group contents, high cationic charges might be formed on the alpha-chitin fibril surfaces in high density by protonation in water at pH 3-4. (c) 2009 Elsevier Ltd. All rights reserved.