Chain polarity transformation from cellulose

The allomorphs and derivatives prepared from cellulose I and II in solid state could be transformed into cellulose I and II, respectively. The memory phenomenon of the original crystal structure should be due to a structural characteristic (chain conformation, chain polarity or others) of an individual chain that is common within each family and kept through the change of crystal structure. There were direct irreversible conversions between corresponding cellulose esters, Na-cellulose and cellulose IV prepared from cellulose I and II just like that between I and II. Accordingly, the structural characteristic should be the cause of the structural irreversibility between the I and II families. 

Accordingly, cellulose has an average molecular weight in the range of 300 000-500 000. One of the most interesting eharacteristics is that eellulose eonsists of several crystal polymorphs, with the possibility of eonversion from one form to another. Its six different polymorphs differ in unit cell dimensions and chain polarity, and are the principle component of all plant cell walls. The natural cellulose I has two different structures, lot and 1(3, while cellulose II is another important crystalline form of cellulose. The transformation of cellulose I to cellulose II is generally considered to be irreversible, because cellulose II is more stable than cellulose I. With proper chemical treatments, it is possible to produce cellulose III and cellulose IV. 

The transformation of cellulose I to cellulose II during mercerization has been suggested to be the result of a progressive shift of the sheets of cellulose chains within the crystallites of a microfibril from the quarter-staggered relationship in cellulose I to the complete correspondence found in cellulose II. Observed changes in lateral discnrder, cell dimensions, swellii, and AT-ray diffraction reflections of cellulose fibres support this theory. Such a shift may occur in the transformation of native celluloses with antiparallel structures as well as those with parallel polarity. 

The major difference between these two crystal structures resides In the chain packing polarity. As expected from the conversion studies and the Irreversibility of the cellulose I to Na-cellulose I transformation, the crystal structure of Na-cellulose I Is based on antiparallel chains (cf. Fig. 3). Because of the presence of Na Ions, which apparently form secondary bonds with the cel-... 

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