INTERFACE BETWEEN MONOCLINIC CRYSTALLINE CELLULOSE AND WATER - BREAKDOWN OF THE ODD EVEN DUPLICITY/

The interface between the (110) crystal face of cellulose I beta and w ater was studied by molecular dynamics simulation with cellulose coord inates refined from electron diffraction data as a starting point. Pot ential energies, pucker parameters, torsion angles, and hydrogen bondi ng have been used for the characterization. Only the topmost layer in the cellulose differs in terms of structure and dynamics from the crys tal bulk, but even these difference are small. At the surface approxim ately half of the cellulose intermolecular hydrogen bonding is lost, b ut this is compensated by hydrogen bonds with water molecules. Much of the difference between even and odd (200) planes disappears at the in terface, except for the orientation of the glucose ring plane. Water d ynamics is retarded by a factor of 2-3 close to the surface. The poten tial energy of water molecules in the first hydration layer is lower b y 2 kJ/mol. The cellulose surface contains about five exposed hydroxyl groups per square nanometer, which accounts for the good hydration of the surface.