Cellulose forms

Solid cellulose forms a microcrystalline structure with regions of high order, i.e., crystalline regions, and regions of low order that are amorphous. Naturally occurring cellulose (cellulose I) crystallizes monoclinic sphenodic. The molecular chains lay in the fiber direction ... 

The first practical CSP derived from polysaccharides is cellulose triacetate (21, Figure 3.10) prepared by Hesse and Hagel in 1973.94,95 Since this derivative was prepared by the heterogeneous acetylation of native microcrystalline cellulose (Avicel) in benzene, it has been postulated that its structure is closely related to that of native cellulose (form I). This has been called microcrystalline cellulose triacetate (CTA-I). CTA-I shows characteristic chiral... 

Chanzy and Peguy (13) were the first to report that cellulose forms a lyotropic mesophase. They used a mixture of N-methyl-morpholine-N-oxide (MMNO) and water as the solvent. Solution birefringence occurred at concentrations greater than 20% (w/w) cellulose. The concentration at which an ordered phase formed increased as the cellulose D.P. decreased. The persistence length of cellulose in MMNO-H2O is not known but presumably it has an extended chain configuration in this solvent. Again the question arises as to what is the relevant axial ratio to be used for cellulose. This will be discussed further below. 

Polysaccharides are composed of many monosaccharides bonded together. Common polysaccharides are cellulose, starch, and glycogen. Cellulose forms the structural material of the cell walls of plants. Cellulose is a polymer of glucose and consists of thousands of glucose molecules linked in an unbranched chain (Figure 16.6). 

When reacted with solutions containing nitric acid and sulfuric acid, cellulose forms various nitrated products depending on the temperature and the concentration of these reactants. 

Nitric acid is produced by the chemical reaction of N204 and water, a small amount of which is present in the cellulose, formed in the course of oxidizing or nitrating cellulose ... 

Kaverzneva [63] and Nevell [61] have detected 1-1.5% of ketone groups (carbonyl groups), among the oxidation products of cellulose formed by oxidation of secondary alcohol groups. 

Apart from plants, certain bacteria, algae, and fungi produce cellulose as well. Amongst the cellulose-forming bacteria, Acetobacter strains - reclassified as the genus Gluconacetobacter - are especially suitable for the formation of cellulose. They are not pathogenic, are commonly found on fruits and fruit products, and can be cultivated under laboratory conditions. 

Moreover, if cellulose-forming bacteria could be cultivated on a large industrial scale, the requirements for cellulose could be satisfied entirely from this source in the future. 

The group of plastics known as regenerated celluloses forms a transition from the natural polymers to the completely synthetically produced plastics. As a converted natural product, regenerated cellulose foil (Cellophane) has formed the basis for the first transparent, flexible packaging for food and tobacco which contributed significantly to the development of the self service shops since the beginning of the 1920s. 

A linear jS-1,4 polymer of D-glucopyranose. Cellulose forms the cell walls of plants and is the major constituent of wood and cotton, (p. 1137)... 

The wood cell consists mainly of cellulose, hemicelluloses, and lignin (see Appendix). A simplified picture is that cellulose forms a skeleton which is surrounded by other substances functioning as matrix (hemicelluloses) and encrusting (lignin) materials. 

Cellulose forms the backbone of many important industrial adhesives (52), Professor David Hon of Clemson University reviews the use of cellulosic adhesives in Chapter 21. 

During the interlude with the Vereinigte Glanzstoff Fabriken, Heuser also published papers on the carbonic acid esters of cellulose (formed from methyl chloroformate and a partially hydrolyzed cellulose), on the degrada-... 

Besides the cellulose structures I-IV and their subclasses, cellulose forms a variety of crystalline complexes. Soda celluloses were mentioned above, and there is an extensive array of complexes with amines [236]. Soda cellulose IV [237] is actually a hydrate of cellulose and contains no sodium (historically, cellulose hydrate meant cellulose II, which is now known to contain no water ). Many cellulose derivatives such as the nitrate (see above) and the triacetate [238] also give diffraction patterns. The most recent analysis of triacetate I shows a single-chain unit cell [239]. 

Cellulosic materials usually form crystal structures in part, and water cannot penetrate the inside of crystalline domains at room temperature. Native celluloses form crystalline microfibrils or bundles of cellulose chains 2-5 nm in width for higher plant celluloses and 15-30 nm for algal celluloses, which are observable by electron microscope. Almost all native celluloses have X-ray diffraction patterns of cellulose I with crystallinity indexes (Cl) 13] of about 40-95 %. 

In addition to having relatively stiff chains, cellulose forms an extensive network of hydrogen bonds (some of which involve water molecules), resulting in the formation of microfibrils from extended chain sheets (Figure 9-35). There are also some amorphous polysaccharides present in a fiber such as cotton and the aggregated microfibrils have extensive pores capable of holding relatively large amounts of water (which makes them useful components of diapers ). 

Cellulose is a highly crystalline polymer composed of D-p-glucose units that are arrayed in chains with a polar axis and directionality (39). The two major crystalline forms of this polymer are native cellulose (form I) and regenerated or mercerized cellulose (form II). The present view is that, for cellulose I, all the chains in a crystal point in the same direction, that is, they are parallel, whereas for cellulose II, the chains in adjacent layers of a crystal are antiparallel (39). 

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