Shape control of cellulose nanocrystals via compositional acid hydrolysis

The current medical technology has constantly demanded novel and advanced materials exhibiting the unique physico-chemical properties but, at the same time, possessing the intrinsic biocompatibility. Natural biomolecules based on materials such as peptide- (or protein-) or DNA/RNA derivatives have been formerly considered. To date, a carbohydrate-derived molecule has been a highlight as a substitute with the prior biomaterials, which suffer from their sequence-dependent immuno-cytoxicity. Of most, cellulose based materials have had a profound interest due to the great mechanical and optochemical properties as well as its immune-friendliness. However, it has been further manipulated in order to get distinctive structures at the desired shape and scale. Here, we report the versatile and synthetic technique to prepare spherical or rod-like cellulose nanocrystals (CNC). Under the varying concentrations of strong sulfuric acids (H₂SO₄) and hydrochloric acids (HCl), spherical or rod-typed CNCs were selectively manufactured via acid hydrolysis of microcrystalline celluloses (MCC) in massive bundles. At the sequential addition of H₂SO₄ and HCl in 1 to 2.5 molar ratios, most interestingly, the spherical CNC alone was observed with the average size of 50 nm in narrow distribution. All of CNCs had the larger surface area with mesoporosity. In addition, it was confirmed by the crystallographic measurement that it was very similar to the maternal structure originating from the bundle celluloses. It is much anticipated that the porous cellulose nanocrystals may play a principal role as a potential drug carrier for diseased biological compartments.