Temperature induced reversible phase transition of native cellulose has been studied by X-ray diffraction and molecular dynamics (MD) simulation. The transition is characterized by drastic increase in distance between pyranose planes, which was observed both experimentally and in MD. Computed trajectories suggested that the phase transition was associated by the conformational change of the exocyclic hydroxylmethyl groups.  By modifying a parameter related to the relative potential energy among different conformers, the phase transition in silico could be made reversible. From the linear dependence of transition temperature and the relative potential energy between conformers, the entropy change due to the phase transition could be estimated to be about 26 JK-1mol-1. The contributions of torsional entropy of each side group was calculated where the hydroxyl groups at O2 and O6 gave 8 JK-1mol-1 each while that at O3 gave 4 JK-1mol-1 and at hydroxymethyl rotation gave 6 JK-1mol-1.

Thermodynamics of the reversible phase transition of cellulose

243rd National Meeting (2012)

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