COMBINED INFRARED AND ELECTRON-DIFFRACTION STUDY OF THE POLYMORPHISM OF NATIVE CELLULOSES

In this study, 10 cellulose samples of various origins were subjected to heat annealing in 0.1 N NaOH at 260-degrees-C. The initial and annealed samples were analyzed by electron diffraction experiments. It was confirmed that the initial samples contained various proportions of I-alpha (triclinic) and I-beta (monoclinic) phases. They could be classified into two families: a family I where the amount of the phase I-alpha was either small or below detection and a family II where this phase was the major component. The annealing treatment revealed that the I-alpha phase was metastable as it could be converted totally to the stable I-beta phase. The conversion I-alpha --> I-beta was also followed by Fourier transform infrared (FT-IR) spectroscopy. Absorption bands near 3240 and 750 cm-1 were assigned to the I-alpha phase whereas bands near 3270 and 710 cm-1 corresponded to the I-beta phase.