Polysaccharides II

This review gives an overview on oxidized functionalities in celluloses, i.e., carbonyl and carboxyl groups, with regard to their chemical structure, the different ways of introduction, and their analytics. Starting from different processes introducing oxidative modifications into celluloses a survey on the chemical nature of these functionalities is given and analytical approaches towards their determination are discussed. Special emphasis is placed on recent developments which combine group-selective fluorescence labeling with multi-detector GPC analysis to provide carbonyl and carboxyl group profiles according to the CCOA and FDAM method, respectively. Examples of monitoring the oxidation state of celluloses and its changes during processing stages are given, for example bleaching, aging, dissolution or irradiation procedures.

Cellulose is a fascinating and almost inexhaustible and sustainable natural polymeric raw material characterized by exciting properties such as hydrophilicity, chirality, biodegradability, broad chemical-modifying capacity, and the formation of different semicrystalline fiber morphologies. If cellulosics such as bacterial cellulose or strongly disintegrated wood cellulose are composed of nanosized fibers and the nanofiber structuring determines the product properties, these polymers are described as nanocelluloses. Because of the extraordinary supramolecular structure and exceptional product characteristics as high-molecular and high-crystalline cellulosics with a water content up to 99%, nanocelluloses require increasing attention. This review assembles the current knowledge in research, development, and application in the field of nanocelluloses through examples. The topics combine selected results on nanocelluloses from bacteria and wood as well as their use as technical membranes and composites with the first long-time study of cellulosics in the animal body for the development of medical devices such as artificial blood vessels, and the application of bacterial nanocellulose as animal wound dressings and cosmetic tissues.

This review surveys advances in current studies of a variety of polymer compositional materials based on cellulose and related polysaccharides, the major studies being directed toward elaborate designs of environmentally conformable and/or biocompatible materials or highly functionalized material systems for many-faceted prospective applications. The scope covers graft copolymerization, miscible or compatible polymer blending and interpenetration, nanohybridization with inorganic minerals, surface modification of matrices, and mesoscopic self-assembling such as the formation of liquid crystals. In each individual case, it will be shown that cellulosic polysaccharides are microscopically incorporated and cooperatively interact with other adequate polymeric or inorganic ingredients to attain some functional objective. However, essential factors are the inherent characteristics of cellulosic polymers, such as the reactivity allowing hydroxyl substitution, hydrogen-bonding formability, complexing ability, semi-rigidity, chirality, etc. Material functionalities arousing interest include highly controllable biodegradability coupled with ease of processing for relatively common use as consumables, and further extensions for special uses, from mechanical and adsorptive performance to use in novel optical, electro-optical, and ion-conductive devices, etc.