Simulation Studies of Confinement of Water Molecules On Crystalline Faces of Cotton Cellulose

Cellulose nanofibers have recently been shown to have a great potential for applications as composite biomaterials. Cellulose crystal surfaces express heterogeneity in their wetting characteristics. While water plays an important role in determining the physical properties of cotton cellulose, excess water can limit their use in nanocomposites. A molecular level understanding of the interaction of various faces of cellulose crystal with water is therefore necessary to optimize the moisture content. We investigate the behavior of water molecules on (110) surface of Iβ cellulose using isochoric molecular dynamics (MD) simulations at room temperature. Partial barrier to the wetting was created by substituting the hydroxyl groups of the monomer with hydrophobic functional groups. While water molecules were effectively confined within the hydrophobic boundaries, they were also observed to bridge the hydrophobic regions on a partially modified surface. The length scales over which the bridging occurs could be calculated by quantifying the fluctuations in water densities near the hydrophobic boundaries and defining a critical contact angle.