Cellulose chemical structures

Figure 16-2. Site specific, amphiphilic nature in cellulose chemical structure...

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 ... 

Moreover, an absorption band near 1375 cm-i is detected and it is assigned to the CH bending vibration present in cellulose and hemicellulose chemical structures (Sim et al., 1998). The prominent band at 1044 cm-i is also associated with hemicelluloses and is attributed to the C-OH bending. Finally, a sharp band at 897 cm-i, which is typical of b-glycosidic linkages between the sugar units in hemicelluloses, was detected in the anomeric region (Sun et al., 2005). 

A modified nucleotide found in RNA sequencing could either be a new nucleotide of unknown chemical structure or it could correspond to an already known modified nucleotide (up to now about 90 different modified nucleotides have been identified in RNA). Keith [124] proposed preparative purifications of major and modified ribonucleotides on cellulose plates, allowing for their further analysis by UV or mass spectrometry. Separation was realized by two-dimensional elution using the following mobile phases (1) isobutyric acid-25% ammonia-water (50 1.1 28.9,... 

These are defined as anionic dyes with substantivity for cellulosic fibres applied from an aqueous dyebath containing an electrolyte. The forces that operate between a direct dye and cellulose include hydrogen bonding, dipolar forces and non-specific hydrophobic interaction, depending on the chemical structure and polarity of the dye. Apparently multiple attachments are important, since linearity and coplanarity of molecular structure seem to be desirable features (section 3.2.1). The sorption process is reversible and numerous attempts have been made to minimise desorption by suitable aftertreatments (section 10.9.5). The two most significant non-textile outlets for direct dyes are the batchwise dyeing of leather and the continuous coloration of paper. 

Fig. 1 Chemical structures of the polymers commonly used for preparation of beads poly (styrene-co-maleic acid) (=PS-MA) poly(methyl methacrylate-co-methacrylic acid) (=PMMA-MA) poly(acrylonitrile-co-acrylic acid) (=PAN-AA) polyvinylchloride (=PVC) polysulfone (=PSulf) ethylcellulose (=EC) cellulose acetate (=CAc) polyacrylamide (=PAAm) poly(sty-rene-Wocfc-vinylpyrrolidone) (=PS-PVP) and Organically modified silica (=Ormosil). PS-MA is commercially available as an anhydride and negative charges on the bead surface are generated during preparation of the beads...

FIGURE 9.20 Chemical structure of cellulose (a), which is a glucose polymer, and xylan (b), a typical component of hemicellulose. 

Figure 3.1 Chemical structures of the current most successfully employed derivatised polysaccharide CSPs. (a) CHIRALPAK AD Amylose tris (3,5-dimethylphenylcarbamate) coated onto a silica support, (b) CHIRALPAK AS Amylose tris [(S)-a-methylbenzylcarbamate] coated onto a silica support, (c) CHIRALCEL OD Cellulose tris (3,5-dimethylphenylcarbamate) coated onto a silica support, (d) CHIRALCEL OJ Cellulose tris (4-methylbenzoate) coated onto a silica support.

The photo-cross-linkability of a polymer depends not only on its chemical structure, but also on its molecular weight and the ordering of the polymer segments. Vinyl polymers, such as PE, PP, polystyrene, polyacrylates, and PVC, predominantly cross-link, whereas vinylidene polymers (polyisobutylene, poly-2-methylstyrene, polymethacrylates, and poly vinylidene chloride) tend to degrade. Likewise, polymers formed from diene monomers and linear condensation products, such as polyesters and polyamides, cross-link easily, whereas cellulose and cellulose derivatives degrade easily. ... 

Melamines have found utility as rotproofing and weatherproofing cellulosics (57,58), as binders for pigments and for transfer printing of cotton and cotton blends (59), as well as in numerous other applications. Guanamines have been suggested for many of the same applications as melamines, but the similar chemical structures of the two are likely to add to the same problems encountered with melamines. 

Xanthan. Xanthan, known commercially as xanthan gum [11138-66-2], has a main chain of (1 — 4)-linked (3-D-glucopyranosyl units therefore, the chemical structure of the main chain is identical to the structure of cellulose [9004-34-6]. However, in xanthan, every other (3-D-glucopyranosyl unit in the main chain is substituted on 0-3 with a trisaccharide unit. The trisaccharide side chain consists of (reading from the terminal, nonreducing end in towards the main chain) a P-D-mannopyranosyl unit linked (1 — 4) to a P-D-glucopyranosyluronic acid unit linked (1 — 2) to a... 

After devoting considerable thought to the problem of the chemical structure of alkali cellulose, Bleshinskil and Lositskaya 0 have suggested... 

As Indian hemp was charred for increasing periods of time, some loss of chemical structure was incurred (Figure 7). The sample charred for 30 minutes is white and fragile, while the 10 and 20 minute samples are still black and fibrous and appear more like the charred fibers observed in the archaeological textiles. It is obvious that the composition has been altered by exposure to heat. The cellulose is dehydrated with the 2900 cm-1 band reduced in each of the levels of charring. The 10 and 20 minute samples are similar to each other, but somewhat different from the uncharred Indian hemp. The 1630 cm-1 band in the uncharred fiber is shifted to 1582 cm-1 due to dehydration. The new bands in the region of 1450 cm-1 and 1200 cm-1 in the 30 minute sample are comparable to those noted by Ercin and Yurum (44). 

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