Preparation of Self-Assembled Chitin Nanofibers by Regeneration from Ion Gels Using Calcium Halide • dihydrate/Methanol Solutions

Preparation of self-assembled chitin nanofibers and their films by regeneration from chitin ion gels using calcium Halide center dot dihydrate/methanol solutions was carried out. First, the ion gel (10.7 wt%) was prepared by immersing a chitin powder in an ionic liquid, 1-allyl-3-methylimidazolim bromide, at room temperature, followed by heating at 80 degrees C according to the method reported previously by us. Then, the regeneration of chitin was conducted by addition of CaCl2 center dot 2H(2)O/methanol solutions (3.06, 1.53 mol/L) or CaBr2 center dot 2H(2)O/methanol solutions (1.53, 0.765 mol/L) as well as methanol to the gel, followed by sonication to produce chitin dispersions. Morphologies of the chitin assemblies at nanoscale in the dispersions were evaluated by SEM measurement. The use of each calcium halide center dot dihydrate/methanol solution in higher concentration for the regeneration did not induce self-assembly to nanofibers, whereas the nanofibers with higher aspect ratio were produced by the regeneration using CaBr2 center dot 2H(2)O/methanol solution in lower concentration (0.765 mol/L). Furthermore, the films were formed by isolation of the chitin assemblies from the dispersions by filtration. The crystalline structures of the regenerated chitins and the absence of calcium halides in the films were confirmed by powder X-ray diffraction measurement and energy-dispersive X-ray spectroscopy using scanning electron microscope. The tensile testing of the films indicated that morphologies of the chitin assemblies in the films strongly affected the mechanical properties.