Cellulose Essay

3.0 Structure and Properties of Cellulose and Nanocellulose Cellulose is a linear chain of glucose molecules having a flat ribbon-like conformation (Figure 3.1). The repeat unit consists of two anhydroglucose rings (C6H10O5)n joined together through an oxygen which is covalently bonded to C1 of one glucose ring and C4 of the adjoining ring (1 - 4 linkage) and called the β 1–4 glucosidic bond (Samir et al,, 2005). The degree of polymerization, n, varies between 10 000 and 15 000, where n is dependent on the cellulose source material. The hydrogen bonding between hydroxyl groups and oxygens of the adjoining ring molecules stabilizes the linkage resulting in the linear configuration of the cellulose chain. During biosynthesis, van der Waals and intermolecular hydrogen bonds between hydroxyl groups and oxygens of adjacent molecules promote parallel stacking of multiple cellulose chains which form elementary fibrils that further aggregate into larger microfibrils which have a diameter of 5–50 nm and length of several microns. The hydrogen bonding (intra- and inter-chain) network makes cellulose a very stable polymer, and imparts high axial stiffness to cellulose

Table 2.3 presents the different methods for characterization of nanocellulose. Information about the shape, mean size, and distribution of size of cellulosic nanoparticles can be obtained by methods such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), or light scattering (Elazzouzi-Hafraoui et al. 2008). TEM is the ultimate tool for assessment of nanofibril morphology as TEM yields images at high-resolution, making it possible to visualise sub-nanometre surfaces (Chinga-Carrasco and Syverud,