Using 1064-nm FT-Raman spectroscopy, detailed analyses of a number of naturally occurring celluloses were carried out and important new information was discovered. The most important information was from the Raman bands representing the CH2 scissoring modes which indicated that in all natural celluloses more-than-one -C(6)H2OH rotational isomers existed simultaneously. And the amounts of the rotamers varied with the source of the cellulose. Moreover, in the samples representative of treated celluloses and lignocelluloses, these rotamer-ratios depended upon the history of the samples. The findings clearly indicated the presence of significant disorder in otherwise ordered cellulose domains and implied that celluloses in their native states of aggregation are not crystalline. Furthermore, FT-Raman analysis of samples of celluloe II, cellulose III, and amorphous celluloses indicated that the -CH2OH rotamers were present exclusively in the gg conformation. This is in stark contrast to the existence of gg, gt, and tg conformations in naturally occurring celluloses (cellulose Is). Existence of different CH2OH conformers has important implications for intra- and inter-molecular H-bonds and therefore, for cellulose chain conformation. In light of the present discovery, a number of experimental outcomes were predicted and were found to be true. The latter included, among other things, failure to generate CNCs from wood, correspondence between the predicted and determined TGA-behavior of various cellulose materials, and observations in relation to cellulose-water interactions. Finally, most existent IR, NMR, and X-ray data on cellulose structures can be successfully accounted for in terms of the new discovery.

Big surprise: Natural cellulose is not crystalline

247th National Meeting (2014)

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