Structure and rheology of nanocrystalline cellulose

Sulfate hydrolysis and high-pressure homogenization were combined to reduce the size of microcrystalline cellulose to the nanoscale. The obtained needle-shaped nanocrystals showed a relative uniform size with length of 90 +/- 50 nm and width of 10 +/- 4 nm. Rheology and phase transition of the nanocrystal colloids were studied. The flowability and modulus of the colloids showed a strong relationship with frequency, temperature, and concentration of the nanocrystals. Nanocrystals self-assembled into a liquid crystal phase in colloids and even in the dried film. Structure and morphology of the ordered liquid crystalline phase were characterized by scanning electron microscope and polarized optical microscope. It was found that cellulose nanocrystals were self-aligned layer by layer, which was responsible for the color of the dried film and also allowed an ordered layered microporous foam from the freeze-dried nanocrystalline colloids. (C) 2010 Elsevier Ltd. All rights reserved.