(167e) Dissolution of Cellulosic Fibers: Effect of Fiber Morphology and Size

Dissolution of cellulose, a nanostructured polymer abundant in nature, is a critical step for the efficient utilization of this renewable resource as a starting material for the synthesis of high value-added functional polymers and chemicals and also for biofuel production.  The recalcitrance of cellulose microfibrils provides the major barrier to solubility of cellulose.  There are a few solvent systems effective for direct dissolution of cellulose, and they operate under rather strict conditions of composition and temperature.  In general, cellulose dissolution depends on its supramolecular and hierarchical structure, physico-chemical properties of solvent, and temperature.  We investigate here the effect of morphology and size of cotton fiber, as the most important natural textile and a highly crystalline form of cellulose, on the mechanism of fiber swelling and dissolution.  To this end, we have developed a phenomenological model for describing the swelling and dissolution of solid cellulosic fibers.  The model considers cellulosic fibers as non-uniform crystalline polymers with different morphological properties among their cross sections due to the different supramolecular and morphological structures of cell-walls.  The model parameters, i.e., the solvent effectiveness in decrystallization of cellulose, and the ability of solvent in cellulose chain untangling, was obtained by fitting to experimental data.  The modeling parameters were then used to examine the influence of fiber size and structure (e.g., degree of polymerization and crystallinity) on the mechanism of dissolution process as well as on the total time required for decrystallization and dissolution of the fiber.  The insights obtained from this model should facilitate the design of efficient solvent systems and processing conditions for woody biomass dissolution.