Abstract
We present the results of Langevin dynamics simulations on a coarse–grained model for crystalline cellulose. In particular, we analyze two different cellulose crystalline forms: cellulose Iβ (the natural form of cellulose) and cellulose IIII (obtained after cellulose Iβ is treated with anhydrous liquid ammonia). Cellulose IIII has been the focus of wide interest in the field of cellulosic biofuels as it can be efficiently hydrolyzed to glucose (its enzymatic degradation rates are up to 5–fold higher than those of cellulose Iβ). In turn, glucose can eventually be fermented into fuels. The coarse-grained model presented in this study is based on a simplified geometry and on an effective potential mimicking the changes in both intracrystalline hydrogen bonds and stacking interactions during the transition from cellulose Iβ to cellulose IIII. The model accurately reproduces both structural and thermomechanical properties of cellulose Iβ and IIII. The work presented herein describes the structural transition from cellulose Iβ to cellulose IIII as driven by the change in the equilibrium state of two degrees of freedom in the cellulose chains. The structural transition from cellulose Iβ to cellulose IIII is essentially reduced to a search for optimal spatial arrangement of the cellulose chains.
