Of the many observations reported in cellulose literature, the phenomena of “cocrystallization” and “moisture-induced shift in XRD” (XRD-shift) need reexamination. Does cocrystallization really occur or, entirely, something else is going on? Recent research carried out in the laboratory of the author (Agarwal et al. 2018 Carbohydrate Polymers 190: 262–270); Agarwal et al. 2016, Cellulose 23:125–144) suggests that upon hydrothermal treatment wood-cellulose becomes crystalline from an arrangement, existing in the native state, where the cellulose is simply organized but not crystalline. The latter accounted for the increased crystallinity and contradicted the reported interpretations based on the increased size of the crystal, as would happen in cocrystallization. Similarly, although the moisture-induced XRD-shift is real, the generally accepted interpretation of the shift is based on an assumption. Namely, that the environmental stresses cause changes in the cellulose crystal. An alternate explanation has been proposed by Agarwal et al., (Cellulose 2017, 24, 1971−1984) wherein the moisture-induced reorganization of cellulose molecules, in the non-crystalline regions, is responsible for the shift. During the presentation, such evidence will be shown and discussed.

Revisiting the phenomena of cocrystallization and moisture-induced shift in XRDs

ACS Spring 2022

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