Cotton cellulose noncrystalline components

Figure 6b shows the spectrum of the crystalline component of cotton soaked in H OCwater content=161%), which was obtained by Torchia s pulse sequence(27,28). The delay time between two ir/2 pulses in the pulse sequence was set to be 100 s. As is clearly seen, the spectrum shown in Figure 6b reflects the components corresponding to the downfield sharp lines of C4 and C6 carbons in the whole spectrum shown in Figure 6a. A similar crystalline spectrum was obtained by others(29) using almost the same technique. On the other hand. Figure 6c indicates the spectrum of the noncrystalline component of the cotton cellulose, which was obtained by subtracting the spectrum of the crystalline component shown in Figure 6b from the whole spectrum shown in Figure 6a. This spectrum evidently corresponds to the components associated with the upfield broad resonances of C4 and C6 carbons.

Figure 10 shows the spectra of the noncrystalline components of cotton cellulose with water contents of 0% and 161%(4), These spectra were obtained by subtracting the spectra of the crystalline components from the corresponding whole spectra as shown in Figure 6. It is clearly seen that the linewidths of the Cl and C4 resonances become markedly narrower upon absorbing water, while holding the chemical shifts unchanged. For instance, the half-value widths of the Cl resonance lines are 50 Hz and 150 Hz, respectively. Such a...

Figure 11 shows the spectra of the noncrystalline components of rayon fibers with the water contents of 0% and 158%( ). In contrast to the case of cotton, the linewidths of the respective resonances do not remarkably decrease by the addition of water for examples, the half-value width of the Cl resonance line is 205 Hz for the hydrated sample, whereas it is 256 Hz for the dry sample. As pointed out above, this fact implies that the molecular mobility of the noncrystalline chains does not greatly increase with the increase of water content. Moreover, the noncrystalline component of rayon does not undergo such a significant change of distributions in torsion angles 4> vjj as observed for cotton cellulose, possibly because the molecular conformation of this component is rather random in the dry state. In other words, such a disordered conformation may hardly allow marked distortion of the noncrystalline chains to be produced upon drying cupra rayon. 

Figure 10 CP/MAS NMR spectra of the noncrystalline components of cotton cellulose with the water contents of 0% (a) and 161% (b). (Reproduced from Ref.4. Copyright 1985 Academia Republicii Soclaliste Romania.)...

Glycol cleavage. The initial periodate oxidation of cellulose, like other chemical reactions, was largely limited to the readily accessible component and has also been used to indicate the accessibility of cellulose substrates [151] (Table 1). Rowland and Cousins [232], based on the influence of periodate oxidation in the crystallinity of cotton, observed about 40% of the component being noncrystalline. Since the m-diol unit is generally more reactive than the /ran.9-diol, the cleavage of the mannose residues would proceed faster than that of the glucose or xylose residues. 

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