- Loukas Petridis, Oak Ridge National Laboratory, Oak Ridge, TN
The full utilization of plant biomass for the production of energy and materials involves high temperature treatment that softens lignin. Examples include melt spinning of lignin for manufacturing low-cost carbon fiber and the relocalization of lignin to increase the accessibility of cellulose for production of biofuels. These temperature0induced changes in lignin arise from an increase in the dynamics of its atoms. Here, we combine molecular dynamics simulations with neutron scattering and dielectric spectroscopy experiments to probe the dependence of lignin dynamics on hydration and thermal history. We find a dynamical hysteresis, in which, at a given temperatures, the dynamics of lignin is faster when the lignin is cooled than when heated. The difference becomes more significant at high temperatures and high hydration levels. The simulations provide a detailed description of the atomic motions and also reveal Syringyl monomers to be more dynamic than Guiacyl. These findings suggest the lignin glass transition, at which the polymer softens, will be lower in the more hydrated environment of plant biomass than for drier, extracted lignin powder.
Please contact Lora Davis (574-6308) for building access.