Structure of Non-Crystalline Domains

Non-crystalline domains (NCD) are other significant constituents of elementary nanofibrils of cellulose. Content of these domains, i.e., degree of amorphicity, influences expressivety on sorption ability, accessibility, reactivity, deformation and some other properties of cellulose materials. The degree of amorphicity (F) can vary from 

0 for hypothetical macrociystals of cellulose to 1 for amorphous sample, e.g., ball-milled cellulose. If Y is expressed in percentage, the natural cellulose can contain 20-35%, mercerized cellulose 45-50% and regenerated cellulose 55-65% of NCD. Lateral size of NCD in elementary fibrils of natural cellulose is close to the size of crystallites, but the length of NCD can be different Unfortunately, X-ray, NMR, spectroscopy and other techniques cannot measure the dimensions of non-crystalline domains. For this purpose the model calculations are used. These calculations are based on the assumption that in the elementary nanofibrils, tbe average length of non-crystalline domain (Lnc) snd crystallite (LJ should be proportional to volume fraction of the constituent. As a result, the following equation was proposed (loelovich, 1999)  

The results showed that the length of non-crystalline areas can be in the range 30 to 60 nm (Table 7.4). Moreover, increasing the length of the crystallites causes decreasing the length of NCD (Fig. 7.8). 

Study of supermolecular structure of NCD is difficult because of disordered structural state of this constituent Method of solid-state CP/MAS C NMR gave a little information about structure of NCD. More informative was method of pulsed proton NMR (Gordeev et al., 1991). By means of this method was established 

the energy of H-bonds in NCD varies from 8 to 26 kj/mol, while the average energy is about 20 kj/mol. 

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