Nematic ordered cellulose

Solid-state cellulose can also be noncrystalline, sometimes called amorphous. Intermediate situations are also likely to be important but not well characterized. One example, nematic ordered cellulose has been described [230]. In most treatments that produce amorphous cellulose, the whole fiber is severely degraded. For example, decrystallization can be effected by ball milling, which leaves the cellulose as a fine dust. In this case, some crystalline structure can be recreated by placing the sample in a humid environment. Another approach uses phosphoric acid, which can dissolve the cellulose. Precipitation by dilution with water results in a material with very little crystallinity. There is some chance that the chain may adopt a different shape (a collapsed, sixfold helix) after phosphoric acid treatment. This was concluded because the cellulose stains blue with iodine (see Figure 5.12), similar to the sixfold amylose helix in the starch-iodine complex. 

The structure of cellulose is closely tied to its synthesis, and although many of the chapters discuss the synthesis of cellulose, the nature of the cellulose product is always kept in mind. A comprehensive account of the structure of cellulose and its polymorphism is provided by French and Johnson, and the structure and properties of a novel form of cellulose (nematic-ordered cellulose) is described by Kondo. Cellulose is the most abundant biomacromolecule in nature, and it is used in a variety of applications. In almost all cases, the applications of cellulose as an industrial material are dependent on its physical and chemical properties. Two chapters discuss novel applications of cellulose. Czaja et al. describe the use of microbial cellulose for applications in wound care and Kim discusses the usefulness of cellulose as a smart material, specifically the production of cellulose-based electroactive paper. 

Current data suggest that cellulose biosynthesis is a bacterial invention and that eukaryotes acquired the process via multiple lateral gene transfers. Bacteria and eukaryota have independently evolved regulatory mechanisms and molecular structures to utilize the p-1,4-homopolymer synthesized by the catalytic activity of homologous cellulose synthase enzymes. The differences in accessory enzymes probably reflect not only convergent evolution to produce a cellulose I crystalline allomorph, but also inventions of alternative products such as cellulose II, noncrystalline cellulose, or nematic ordered cellulose. 

The authors developed a unique form of i-glucan association, nematic ordered cellulose (NOC) that is molecularly ordered, yet noncrystalline. NOC has unique characteristics in particular, its surface properties provide with a function of tracks or scaffolds for regulated movements and fiber production of Acetobacter xylinum (=Gluconacetobacter xylinus), which produces cellulose ribbon-like nanofibers with 40-60 nm in width and moves due to the inverse force of the secretion of the fibers (Kondo et al. 2002). This review attempts to reveal the exclusive superstructure-property relationship in order to extend the usage of this nematic-ordered cellulose film as a functional template. In addition, this describes the other carbohydrate polymers with a variety of hierarchical nematic-ordered states at various scales, the so-called nano/micro hierarchical structures, which would allow development of new functional-ordered scaffolds. 

STRUCTURE OF NEMATIC ORDERED CELLULOSE 2.1 What is nematic ordered cellulose NOC ... 

Figure 16-5. Atomic force micrographs showing the surface of the nematic ordered cellulose (NOC) template with a schematic representation...

Another type of nematic ordered cellulose honeycomb-patterned cellulose... 

Kondo T., Togawa E., and Brown, Jr. R.M. 2001. Nematic ordered cellulose a concept of glucan chain association. Biomacromolecules 2 1324-1330. 

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