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 paper provides an overview of recent progress made in the area of cellulose nanofibre-based nanocomposites. An introduction into the methods used to isolate cellulose nanofibres (nanowhiskers, nanofibrils) is given, with details of their structure. Following this, the article is split into sections dealing with processing and characterisation of cellulose nanocomposites and new developments in the area, with particular emphasis on applications. The types of cellulose nanofibres covered are those extracted from plants by acid hydrolysis (nanowhiskers), mechanical treatment and those that occur naturally (tunicate nanowhiskers) or under culturing conditions (bacterial cellulose nanofibrils). Research highlighted in the article are the use of cellulose nanowhiskers for shape memory nanocomposites, analysis of the interfacial properties of cellulose nanowhisker and nanofibril-based composites using Raman spectroscopy, switchable interfaces that mimic sea cucumbers, polymerisation from the surface of cellulose nanowhiskers by atom transfer radical polymerisation and ring opening polymerisation, and methods to analyse the dispersion of nanowhiskers. The applications and new advances covered in this review are the use of cellulose nanofibres to reinforce adhesives, to make optically transparent paper for electronic displays, to create DNA-hybrid materials, to generate hierarchical composites and for use in foams, aerogels and starch nanocomposites and the use of all-cellulose nanocomposites for enhanced coupling between matrix and fibre. A comprehensive coverage of the literature is given and some suggestions on where the field is likely to advance in the future are discussed.

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Review: current international research into cellulose nanofibres and nanocomposites

Homogeneous suspensions of individualized microfibrils from TEMPO-catalyzed oxidation of native cellulose.

http://pubs.acs.org/doi/pdf/10.1021/bm800038n

Cellulose nanopaper structures of high toughness.

A preliminary experiment has shown that a sheet-shaped material prepared from bacterial cellulose has remarkable mechanical properties, the Young's modulus being as high as >15 GPa across the plane of the sheet. The mechanical properties were little affected by the fermentation conditions of pellicles and the preparation conditions of the sheets, i.e. the pressing and drying of pellicles. From structural investigations, the high Young's modulus has been ascribed to the unique super-molecular structure in which fibrils of biological origin are preserved and bound tightly by hydrogen bonds. It has also been found that a “pulp” obtained from bacterial cellulose gives a strong paper and is useful for reinforcing conventional pulp papers and enabling paper-making from some fibrous materials.

The structure and mechanical properties of sheets prepared from bacterial cellulose

A sheet obtained from bacterial cellulose had a remarkably high modulus of elasticity as reported in Part 1 of this series. The Young's modulus of a sheet prepared by squeezing and drying a gel-like pellicle of bacterial cellulose was found to be >15 GPa. In addition, it has been found that treatment of the gel-like pellicles or dried sheets of bacterial cellulose with alkaline and/or oxidative solutions improves the mechanical properties significantly, and the Young's modulus of the resulting sheets approaches 30 GPa. In this paper, improvement of the mechanical properties of bacterial cellulose sheets by the removal of impurities is investigated and the applicability of bacterial cellulose to diaphragms of electroacoustic transducers is discussed

The structure and mechanical properties of sheets prepared from bacterial cellulose Part 2 Improvement of the mechanical properties of sheets and their applicability to diaphragms of electroacoustic transducers

A new substrate for mammalian cell culture was developed using a cellulose membrane produced by Acetobacter aceti Modification of the ionic charge of the membrane and adsorption of collagen to it promoted cellular adhesion to the membrane surface The growth of eight kinds of cells on the membrane, was comparable to that achieved in plastic Petri dishes The membrane was tested for use in the production of recombinant Erythroid Differentiation Factor (EDF)/activin A using genetically engineered Chinese hamster ovary cells Both the viability of the cells and production of EDF/activin A were maintained for about 1 month, while cultures on plastic dishes lasted only 12 days It was considered that the mechanism of improved cell viability was related to the ultrastructure of the cellulose membrane

A new bacterial cellulose substrate for mammalian cell culture. A new bacterial cellulose substrate.

Acetobacter produces a gelatinous membrane composed of a cellulose network when grown in liquid culture under static conditions. The oxygen tension in the gaseous phase was found to have an effect on cellulose production and on the physical properties of the membrane. Cellulose production was higher at oxygen tensions of 10% and 15% than that under atmospheric conditions. In contrast, cell growth remained constant under a variety of oxygen tensions. Unexpectedly, the density of the cellulose network was found to be inversely proportional to the level of cellulose production by cells in the membrane through electron microscopic examination and other studies. It was concluded that this interesting phenomenon can be explained by our previously proposed model of BC network formation.

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Effects of oxygen tension in the gaseous phase on production and physical properties of bacterial cellulose formed under static culture conditions

A new route of preparation of high quality of graphitized films has been demonstrated Highly graphitized films with electrical conductivity as high as 6×103 S/cm have been prepared by pyrolysis of bacterial cellulose films at 2900 °C These films can be well intercalated with acceptors and donors such as FeCl3 and K, resulting in the enhancement of conductivity Temperature dependencies of thermoelectric power and electrical conductivity are similar to those of soft carbon

Kunihiko Watanabe

Papers

The structure and mechanical properties of sheets prepared from bacterial cellulose

The structure and mechanical properties of sheets prepared from bacterial cellulose Part 2 Improvement of the mechanical properties of sheets and their applicability to diaphragms of electroacoustic transducers

A new bacterial cellulose substrate for mammalian cell culture. A new bacterial cellulose substrate.

Effects of oxygen tension in the gaseous phase on production and physical properties of bacterial cellulose formed under static culture conditions

Graphite film prepared by pyrolysis of bacterial cellulose