As the most important skeletal component in plants, the polysaccharide cellulose is an almost inexhaustible polymeric raw material with fascinating structure and properties. Formed by the repeated connection of D-glucose building blocks, the highly functionalized, linear stiff-chain homopolymer is characterized by its hydrophilicity, chirality, biodegradability, broad chemical modifying capacity, and its formation of versatile semicrystalline fiber morphologies. In view of the considerable increase in interdisciplinary cellulose research and product development over the past decade worldwide, this paper assembles the current knowledge in the structure and chemistry of cellulose, and in the development of innovative cellulose esters and ethers for coatings, films, membranes, building materials, drilling techniques, pharmaceuticals, and foodstuffs. New frontiers, including environmentally friendly cellulose fiber technologies, bacterial cellulose biomaterials, and in-vitro syntheses of cellulose are highlighted together with future aims, strategies, and perspectives of cellulose research and its applications.

Cellulose: Fascinating Biopolymer and Sustainable Raw Material

This critical review provides a processing-structure-property perspective on recent advances in cellulose nanoparticles and composites produced from them. It summarizes cellulose nanoparticles in terms of particle morphology, crystal structure, and properties. Also described are the self-assembly and rheological properties of cellulose nanoparticle suspensions. The methodology of composite processing and resulting properties are fully covered, with an emphasis on neat and high fraction cellulose composites. Additionally, advances in predictive modeling from molecular dynamic simulations of crystalline cellulose to the continuum modeling of composites made with such particles are reviewed (392 references).

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Cellulose nanomaterials review: structure, properties and nanocomposites

Cellulose fibrils with widths in the nanometer range are nature-based materials with unique and potentially useful features. Most importantly, these novel nanocelluloses open up the strongly expanding fields of sustainable materials and nanocomposites, as well as medical and life-science devices, to the natural polymer cellulose. The nanodimensions of the structural elements result in a high surface area and hence the powerful interaction of these celluloses with surrounding species, such as water, organic and polymeric compounds, nanoparticles, and living cells. This Review assembles the current knowledge on the isolation of microfibrillated cellulose from wood and its application in nanocomposites; the preparation of nanocrystalline cellulose and its use as a reinforcing agent; and the biofabrication of bacterial nanocellulose, as well as its evaluation as a biomaterial for medical implants.

Nanocelluloses: A New Family of Nature-Based Materials

This article attempts to bring together basic and complex information which has been gathered on cellulose structure, principally that of native cellulose, over the last few decades. Even though advances have been made in the field of crystallography, powder crystallography cannot yield a definitive cellulose structure and single crystal diffraction is not possible due to the lack of suitable crystals. Knowledge obtained on the biosynthesis of native cellulose and on the polymorphy of cellulose and its derivatives help our understanding of ultrastructure. Many inconsistencies between early crystallographic studies of native cellulose have been clarified by the discovery that two polymorphs (α and β) of cellulose I exist. Models of the possible ultrastructural arrangements within native cellulose have been put forward over the decades; with advancement in technology, computer simulations of small and large systems are being created to test the viability of these ultrastructural models. It is hoped that this review will aid in the understanding of the complexity and uncertainties that still exist in this subject

Cellulose: the structure slowly unravels

https://pubs.rsc.org/en/Content/ArticlePDF/2013/GC/C2GC36364J

Deconstruction of lignocellulosic biomass with ionic liquids

Structure formation of regenerated cellulose materials from NMMO-solutions

Supramolecular structure of initially wet bacterial cellulose of Acetobacter xylinum has been investigated by X-ray scattering including synchrotron radiation, transmission electron microscopy, and 13 C-CP/MAS-NMR-spectroscopy. As a result a model is given of never dried swollen microfibrillar ribbons consisting of 5 to 12 waterfree I α ,-crystalline subunits with a cross-section of about 7 nm x 13 nm and of water solvating the subunits. Lateral aggregation of these crystalline units was found along the smaller (110)-lattice planes with a layer of water between adjacent crystallites. The NMR-spectrum of wet bacterial cellulose exhibits an additional C-1 line component indicating cellulose-water interactions. During drying lateral dimensions of the microfibrillar ribbons, crystallite sizes, as well as the overall crystalline order decrease, whereas the I α /I β -ratio of about 80/20 remains approximately unchanged. Conclusions were drawn with regard to the early states of structure formation of bacterial cellulose.

Investigation of the supramolecular structure of never dried bacterial cellulose

Die Mikrofibrillarsturktur von Algencellulose, Bakteriencellulose, Ramie, Baumwollinters und Chemiezellstoff wurde mittels Elektronenmikroskopie und Rontgen-Weitwinkelstreuung vergleichend untersucht. In Abhangigkeit von der Herkunft der Cellulose werden elektronmikroskopicsch Mikrofibrillen mit unterschiedlichen Merkmalen und Lateralen Abmessungen zwischen 4nm und 95 nm gefunden. Mit Hilfe der Rontgen-Weitwinkelstreuung wurden laterale Kristallitabmessungen und erstmalig an Cellulose-I-Proben (Valonia, Ramie) zusatzlich laterale Gitterstorungen auf der Grundlage einer Fourier-Reflexprofilanalyse ermittelt. Die mittleren lateralen Abmessungen der Kristallite als Subbaueinheiten der Mikrofibrillen variieren zwichen 4nm fur Holzzellstoff und 10 nm fur Valonia-Cellulose, Modell vorstellungen zur Feinstruktur der Mikrofibrillen wurden anhand der Ergebnisse kritisch diskutiert.



The Microfibrillar structure of algae cellulose, bacterial cellulose, ramie, cotton linters, and dissolving pulp samples were investigated by electron microscopy and X-ray diffraction. The microfibrils as detected by means of electron microscopy show different features and lateral dimensions from 4 nm to 95 nm depending on the source of the cellulose. Lateral crystallite dimensions have been obtained by wide angle X-ray diffraction. Using a Fourier method for peak profile analysis separate determinations of lateral crystallite size and lattice distortions are given for the first time for cellulose I samples (valonia, ramie). The mean lateral dimensions of the crystallites, being subunits of the microfibrils, vary between 4 nm for pulp and 10 nm for valonia cellulose. Models of the supermolecular structure of the fibrils have been discussed critically.

Zur Fibrillarstruktur nativer Cellulose

The invention pertains to a process for manufacturing cellulosic moldings wherein a solution containing cellulose dissolved in amine oxides is molded in a die and the molded solution is fed through an air zone into a regenerating medium The molded solution is passed successively through at least two regenerating media, which are selected so that a slower coagulation takes place at least in the first regenerating medium than in the final regenerating medium

Cellulosic molding process and cellulosic moldings

The shaping of cellulose from NMMO solution opened up new possibilities of the manufacturing of cellulose fibers and films with properties different from conventional products. Using electron microscopy and X-ray scattering, structural particularities of the new fibres were shown and it was demonstrated that the property profile of this kind of fibres can be modified by skin-core structures. Blown films from cellulose were characterised with regard to the cross-sectional morphology as well as to the orientation of crystalline regions. Micrographs show that the pore structure and the network density of the cellulose phase can be varied in a wide range up to an asymmetrical cross-sectional structure. By pole figures obtained from X-ray scattering it was shown that the uniplanar-axial texture of the films can be controlled in a wide range, thus allowing to adjust the mechanical properties in machine direction and transversely. Finally, investigations of new thermoplastic, biodegradable cellulose derivatives and of blends with these materials were performed. Results with regard to the supramolecular order and the blend morphology were reported.

Hans Joachim Purz

Papers

Structure formation of regenerated cellulose materials from NMMO-solutions

Investigation of the supramolecular structure of never dried bacterial cellulose

Zur Fibrillarstruktur nativer Cellulose

Cellulosic molding process and cellulosic moldings

Strukturelle Aspekte neuer Cellulosematerialien