Mercerized cellulose hydrogen bonding patterns

Once dehydrated, the microfibrils are practically without functionality in ordinary food processing and preparation operations, because the inert microcrystallites are difficult for water to penetrate. The polymorphs, cellulose I and II (Blackwell, 1982 Coffey el al., 1995), are differentiated by their molecular orientation, hydrogen-bonding patterns, and unit-cell structure. Cellulose I is the natural orientation cellulose II results from NaOH treatment under tension of cellulose I with 18-45% alkali (mercerization). The I—II transition is irreversible. Mercerization strengthens the fibers and improves their lustre and affinity for dyes (Sisson, 1943). Sewing thread was relatively pure mercerized cotton until the advent of synthetic polymer fibers. 

Cellulose polymorphy was studied by comparing the spectra of Valonia, ramie, and mercerized ramie. It appears that the conformation of the cellulose backbone is the same in Valonia and ramie celluloses, but that the hydrogen bonding patterns are different. Mercerized cellulose and native celluloses differ in both their backbone conformations and hydrogen bonding patterns. 

An unusual pattern of dissolution of cellulose and related polysaccharides in the S02-amine-DMS0 system has been observed, and interpreted in terms of distinctive hydrogen bonding patterns. In particular, it was found that only native and mercerized cellulose dissolve in this system, while regenerated celluloses, glucoman-nan, xylan, starch, pectin and curdlan are insoluble. 

Our proposal has the key implication that regenerated and mercerized celluloses have different patterns of intermolecular hydrogen bonding, even though they may have similar heavy atom lattices. This is analogous to what has been proposed as the key difference between... 

In the previous work in which (H- and )3c-NMR were used (17), the dissolution of cellulose in the SO2-DEA-DMSO system has been explained in terms of complex formation between the -OH of cellulose, and SO2 and DEA, as shown in Figure 1. The pattern of solubilities noted earlier suggests that the complex formation reaction in Figure 1 is specific to particular intra- and/or intermolecular hydrogen bonding patterns peculiar to native and mercerized celluloses. 

Native and mercerized celluloses would seem to have some coimnon hydrogen bonding patterns, although they have different x-ray diffraction patterns. On the other hand, mercerized and regenerated celluloses would differ from each other with respect to intermolecular hydrogen bonds, although they have the same x-ray pattern. 

Recently, VanderHart and Atalla (18) proposed,on the basis of CP-MAS 13c KMR of different cellulose samples, that all native cellulose are composites of two crystalline modifications, cell Ijj and Ig, even though they have similar x-ray patterns. These have been interpreted in terms of similar heavy atom lattices with different hydrogen bonding patterns (19,20). Thus, it may well be that mercerized and regenerated celluloses differ in the same way and can have different intermolecular hydrogen bonding patterns, which result in differences in their solubility in the SO2-DEA-DMSO system. 

Cellulose III. Cellulose III results from treatment of cellulose with Hquid ammonia (ammonia mercerization) or amines. Cellulose III can be made from either Cellulose I or II. When treated with water. Cellulose III can revert to its parent stmcture. Some cellulose III preparations are much more stable than other preparations. The intensities on diffraction patterns from Cellulose III differ slightly depending on whether the Cellulose III was made from Cellulose I or II, and thus these allomorphs are called IIIj or IHjj- Workers studying III concluded, based partiy on the results of I and II, that the packings of IIIj and IIIjj are parallel and antiparallel, respectively (67). IIIjj also is thought to have hydrogen bonds between the corner and center chains. 

During our studies on cellulose chemistry ), we have encountered an unusual pattern of solubilities of various celluloses and related polysaccharides in one of the nonaqueous cellulose solvent systems we investigated, the S02-diethylamine(DEA)-dimethyl-sulfoxide(DMSO) system. In this paper, we propose an interpretation of this pattern in terms of intra- and intermolecular hydrogen bonds in native, mercerized and regenerated celluloses. We also consider parallels with the relative reactivities of hydroxyl groups in glucose residues of cellulose toward etherification, under basic conditions, and the data from solid-state C-NMR reported by Atalla and others ( - ) ... 

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