The shape and size distribution of crystalline nanoparticles resulting from the sulfuric acid hydrolysis of cellulose from cotton, Avicel, and tunicate were investigated using transmission electron microscopy (TEM) and atomic force microscopy (AFM) as well as small- and wide-angle X-ray scattering (SAXS and WAXS). Images of negatively stained and cryo-TEM specimens showed that the majority of cellulose particles were flat objects constituted by elementary crystallites whose lateral adhesion was resistant against hydrolysis and sonication treatments. Moreover, tunicin whiskers were described as twisted ribbons with an estimated pitch of 2.4-3.2 microm. Length and width distributions of all samples were generally well described by log-normal functions, with the exception of tunicin, which had less lateral aggregation. AFM observation confirmed that the thickness of the nanocrystals was almost constant for a given origin and corresponded to the crystallite size measured from peak broadening in WAXS spectra. Experimental SAXS profiles were numerically simulated, combining the dimensions and size distribution functions determined by the various techniques.

Cotton cellulose nanocrystals with different aspect ratios have been dispersed in cyclohexane as a model apolar solvent, using surfactants. Above a critical concentration, which was higher than that in water, the suspensions spontaneously phase separated into a chiral nematic mesophase. According to Onsager's theory, the phase separation is controlled by the aspect ratio, while being influenced by the polydispersity. The sample with the highest aspect ratio did not show any phase separation but instead shows an anisotropic gel phase at high concentration. Experimental critical concentrations were found to be much lower than the predicted ones, revealing an attractive interaction between the rods. Chiral nematic pitches as small as 2 mum were found to be much lower than those measured in water, due to stronger chiral interactions in the apolar medium.