We report recent advances in understanding how structure of higher plant cellulose deviates from the Iα and Iβ crystal structures, which represent models of perfect cellulose crystals. In the first part of this work, we consider a type of crystallographic defect known as stacking fault [1]. This type of defect is defined by Iα-like molecular layers existing within Iβ crystals. We present diffraction patterns calculated from crystals with stacking faults and show that such patterns compare favorably with experimental data. The proposed stacking faults bring a novel interpretation for Iα-Iβ coexistence in higher plant cellulose. In the second part of the work, we investigate the nature of cellulose crystal-crystal interfaces, which are inherent to formation of cellulose crystal aggregates. A geometric model of these interfaces is proposed with basis on results from X-ray diffraction and moisture sorption analyses performed across wide spectrum of celluloses isolated from higher plants [2]. Furthermore, a novel analytical technique - infrared spectroscopy associated with dynamics of deuterium exchange - has been developed to selectively probe such interface regions [3]. First results from this novel technique are presented, bringing valuable information to understand cellulose supramolecular structure in crystal-crystal interface regions. [1] Driemeier, C.; Francisco, L. H. Cellulose 2014, 21, 3161–3169. [2] Driemeier, C.; Bragatto, J. J. Phys. Chem. B 2013, 117, 415–421. [3] Driemeier et al. (in preparation).

Imperfections in higher plant cellulose: Crystal stacking faults and structure of crystal-crystal interfaces

249th National Meeting (2015)

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