Investigation of Lignin-water interactions by molecular simulation

The results of molecular dynamics simulations of three lignin-water systems are presented. Static and dynamic properties of each system are compared to a benchmark system consisting entirely of water molecules. The significantly reduced mobility of water molecules local to lignin hydroxyl regions is attributed to hydrogen bond formation, while the slightly reduced mobility of water molecules in the vicinity of lignin methoxyl groups results from a hydrophobic effect that causes water molecules to structure themselves around these groups. The average diffusion of water in each system correlates with the number of methoxyl groups present in the system. As the number of methoxyls in the system increases, so too does the average diffusion constant of water in that system. The bulky methoxyl groups obstruct water from accessing lignin hydroxyl regions where hydrogen bond formation is anticipated and the hydrogen-bonded water lowers the average diffusion constant.