Combination of X-ray and neutron diffraction techniques has demonstrated the hydrogen bond disorder in highly crystalline native cellulose, yielding two possible hydrogen bond networks. Nevertheless, based on the same experimental techniques, no similar disorder was found in cellulose II and IIII. MD simulations, using four carbohydrate force fields (GROMOS, CHARMM, GLYCAM, OPLS), together with dispersion-corrected DFT calculations favor an alternative, energetically more stable hydrogen bonding network, for both cellulose II and IIII, different from the current model based on neutron fiber diffraction data. Energy analysis shows that the alternative model was stabilized by intramolecular factors rather than hydrogen bonds in agreement with the population analysis in the crystal structure database. Diffraction patterns calculated from the DFT optimized models were compared with the experimental ones, to directly estimate the reliability of the models. We found that for cellulose II the current experimental model reproduced better the experimental diffraction pattern, while a subtle difference was in support of the energetically determined cellulose IIII model.

Energetically favored alternative hydrogen bond of cellulose II and cellulose IIII

249th National Meeting (2015)

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