Cellulose: Structure and Properties

Cellulose, a fascinating biopolymer and the most common organic compound on earth, is comprehensively reviewed. Details of its crystalline phases are given, starting with a description of molecular and supramolecular structures, including the hydrogen bond systems. Sources of this ubiquitous biopolymer are mentioned, with attention to the special properties of bacterially synthesized nanofibrous cellulose. Nanostructures obtained by disintegration of cellulose fibers (top-down approach) yielding nano- or microfibrillated cellulose and cellulose whiskers are the basis for novel materials with extraordinary properties. Moreover, nanofibers and nanoparticles can be made by special techniques applying the bottom-up approach. Efficient systems to dissolve cellulose by destruction of the hydrogen bond systems using ionic liquids and systems based on polar aprotic solvent and salt are described. Novel cellulose derivatives are available by chemical modification under heterogeneous or homogeneous conditions, depending on the cellulose reactivity. In particular, unconventional nucleophilic displacement reactions yielding products for high-value applications are highlighted. Novel amino cellulose derivatives showing fully reversible aggregation behavior and nanostructure formation on various materials are the focus of interest. Finally, “click chemistry” for the synthesis of novel cellulose derivatives is discussed.