Cellulose is one of the most abundant renewable resources and the research for the application of it as a future energy and new materials has been performing for long years. However, there still exist some unsolved problems even in the basic properties of it. One of such problem is the solubility of cellulose in water. Although cellulose has three hydroxyl groups in each glucose residue, cellulose is hardly dissolved in water except the small size of oligomers of cellulose. The glucose and cellobiose are easily dissolved in water. However, oligomer of cellulose with around heptamer glucose units become hardly be dissolved in water. In this work, molecular dynamics simulation of oligomer cellulose with 2, 4, 6, 8, 10 glucose units has been performed in water environment with GROMACS molecular dynamics program. By using the trajectories of the results, the free energy of solvation of oligomers in water was calculated using Ermod method. The free energies of the solubility were also evaluated by estimating the free energy change during the dissolution processes. The results of the calculated free energy of the solubility well reproduced the experimental behavior of the solubility of the cellulose oligomers. To evaluate the ratio of the contribution of the entropy and the enthalpy on the solvation of oligomers in water, molecular dynamics simulations of oligomers were also performed in different temperatures. From the temperature dependence of the solvation free energies, the contributions of these two terms were evaluated.

Free energy calculation of the solubility of cellulose oligomers in water

254th National Meeting (2017)

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