Crystallinity and nanostructure of cellulose from different sources

Atomic force microscopy (AFM) and Fourier transformation infrared (FT-IR) spectroscopy was used for assessment of structural differences of celluloses of various origins. Investigated celluloses were: bacterial celluloses cultured in presence of pectin and/or xyloglucan, as well as commercial celluloses and cellulose extracted from apple parenchyma. The crystallinity index (XC%) varied from 25 % for apple cellulose to 53 % for microcrystalline commercial cellulose. Significant differences in geometrical dimensions of cellulose microfibrils examined by means of atomic force microscope were observed. Roughness analysis of the AFM topographies profiles showed that the smallest dimensions of the microfibrils had cellulose from apple cell walls in comparison with cotton and bacterial cellulose. Differences between cotton and bacterial cellulose were slighter. Celluloses from studied materials had different elastic characteristics after hydration but almost no differences were found in dry state. Significant dependence between cellulose microfibrils geometry and degree of crystallinity was found. Materials with smaller microfibrils diameters were more amorphous than materials with thicker microfibrils. Nano-structural characterization of cellulose from different sources let to explain various behavior of these materials in macro-scale, e.g. different swelling capacity or tension strength. Quantitative description of the nanostructure properties of cellulose may give useful information for scientific and industrial postharvest technology groups.