Comparative Study of Powder Celluloses and Cellulose Hydrogels by Waxs Method. Impact of Measurement Technique and Computation on Variability of Results

Abstract

A comparative study of crystallinity and size of cellulose crystallites of powder celluloses from hardwood pulp, flax fibers and cellulose hydrogels was performed by the wide-angle X-ray scattering method (WAXS). Cellulose hydrogels were prepared by regeneration from solutions of powder celluloses in DMAc/LiCl. The variation in the structural characteristics of the swollen hydrogels and the freeze-dried hydrogels, alongside the powder celluloses, was studied. The swollen hydrogels contained over 97 mass% water, and thus their WAXS patterns resembled those of water. The WAXS patterns for both powder celluloses indicated cellulose I structure, whereas the freeze-dried hydrogels revealed cellulose II polymorph. The impact of the calculation mode on the obtained crystallinity values was investigated using three analysis methods. The Segal method could be used only for cellulose I samples, whereas amorphous fitting and amorphous subtraction methods could be applied for both samples, cellulose I and II. The Segal method gave the highest crystallinity values, while the amorphous fitting and the amorphous subtraction generated similar values. The advantages of using the amorphous fitting method and the effect of drying on the structure of the hydrogels were discussed.