Molecular structure of cellulose

Streptomycin, chemistry of, 3, 337-384 Structural chemistry, of fungal polysaccharides, 23, 367-417 of the hemicelluloses, 14, 429-468 Structure, molecular, of cellulose, 19, 219-246 of dextran, 15, 341-369 of glycogens, 12, 261-298 of polysaccharide gels and networks,... 

There has been another proposal that plane-structures consisting of cellulose molecules in the lOl plane of native cellulose are held together by hydrophobic interactions even in the presence of alkali, and that hydrophilic surfaces of the 101 plane-structures are solvated with alkali and water (24). However, if such planar structures were solvated with aqueous alkali, they would be expected to result in the formation of a dispersion of micelles. It seems to us more likely that some strong or sterically protected inter-molecular hydrogen bonds of native cellulose survive even in alkali cellulose. On the other hand, since some hydrogen bonds are cleaved by NaOH and water which penetrate into the crystalline lattice of cellulose, new lattice planes can be formed as, for example, in Na-Cellulose I or other soda celluloses. 

The mechanisms of formation and the structural characteristics of cellulose acetate membranes for reverse osmosis have been investigated. Scanning electron microscopy studies showed the membranes to be high molecular weight condensation structures of the cellular type. 

Nitrocellulose, of the resins used in these end uses and in car refinishing, is the nitrate ester of cellulose. The structure is linear and a wide range of (high) molecular weights is available as well as various degrees of nitration ... 

The molecular structure of cellulose, unlike that of starch, allows for strong hydrogen bonding between polymer chains. This results in the formation of strong water-resistant fibers such as those found in cotton, which is 98% cellulose. Cotton actually has a tensile strength greater than that of steel. The major industrial source of cellulose is wood ( 50% cellulose). 

Cellulose is an important part of woody plants, occurring in cell walls and making up part of the structural material of stems and trunks. Cotton and flax are almost pure cellulose. Chemically, cellulose is a polysaccharide—a polymer made by successive reaction of many glucose molecules giving a high molecular weight (molecular weight ->- 600,000). This polymer is not basically different from the polymers that were discussed in Section 18-6 ... 

It is evident that the solid-state NMR data combined with vibration spectra call for a reasessment of earlier views of cellulose I and II. Furthermore, earlier interpretations of diffractometric data that ignore differences in molecular conformations will, according to Atalla 191 be insensitive to subtle structural variations which are central to the phenomena of polymorphy and so clearly indicated by the NMR... 

Fig. 2 Schematic representation of cellulose structures in solution Part A shows the fringed micellar structure. Parts B and C show possible chain conformations of celluloses of different DP. For high molecular weight cellulose, C, intra-molecular hydrogen bonding is possible...

Aquifer bioremediation, defined, 3 758t Aquifer flow, 12 842 Aquifers, 12 838-839 Aquifer sparging, defined, 3 758t AraA [9-(P-D-arabinofuranosyl)-9H-purin-6-amine], 4 713 Arabidopsis, molecular genetics of cellulose biosynthesis, 5 366 Arabinanase, 10 300 Arabinans, classification by structure, 4 723t... 

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