Comparative characterization of aqueous dispersions and cast films of different chitin nanowhiskers/nanofibers

Water dispersions of TEMPO-oxidized alpha-chitin nanowhisker (TOChN), partially deacetylated alpha-chitin nanowhisker/nanofiber mixture (DEChN), HCl-hydrolyzed chitin nanowhisker (HHChN) and squid-pen beta-chitin nanofiber (SQChN) were prepared, and the properties of nano-dispersions and their cast films were characterized between the four chitin nano-samples. Because SQChN has the highest aspect ratio, its 0.1% dispersion had the highest shear stress and viscosity at the same shear rate in the four chitin nano-samples, and showed gel-like behavior in the whole shear rate range from 10(-3) to 10(3) s(-1). AFM images of the self-standing films showed that film surfaces consisted of characteristic chitin nano-elements with different morphologies and degrees of orientation between the four chitin samples, whereas all chitin nanowhisker/nanofiber films had similar thermal degradation points at similar to 200 degrees C. The DEChN film had the highest tensile strength of similar to 140 MPa, elongation at break of similar to 10% and light-transmittance of 87% at 400 nm. In contrast, the SQChN film had the lowest tensile strength, Young's modulus and light-transmittance. All chitin nanowhisker/nanofiber films had similar oxygen permeabilities of similar to 1 mL mu m m(-2) day(-1) kPa(-1), which was clearly lower than that (184 mL mu m m(-2) day(-1) kPa(-1)) of a poly(lactic acid) film. (C) 2011 Elsevier B.V. All rights reserved.