Solubilization of biopolymers by ionic liquids and their mixtures: spectroscopic and thermodynamic approach

Abstract

Research on the dissolution and processing of cellulose by ionic liquids (IL) has progressed significantly, leading to the emergence of industrial applications using this medium. To increase efficiency and lower the costs associated with the process new strategies are required. Therefore, the rationale to achieve this goal is a deep understanding of how the intermolecular interactions govern the thermodynamics and the kinetics of the dissolution process. It is well-known that the basicity of the anion is crucial to determine the capacity of ionic liquids in breaking the strong hydrogen bonds within the cellulose fibers. Also, it was established the importance of the cation in defining the dissolution capacities due to its interaction with the oxygen atoms of the cellulose OH groups. In order to have a greater range of properties, viable alternatives involving IL and their mixtures with molecular solvents or other IL have emerged. Although significant advances were made in this field, there are still major challenges in the understanding of how the delicate balance between all the interactions determines the feasibility of the dissolution process. Therefore, the objective of this project is to comprehensively understand the effects of IL composition and processing conditions on cellulose dissolution, considering cellulose as the most abundant biopolymer in nature and a promising source of clean energy. Our approach involves conducting significant thermodynamic measurements and spectroscopic analyses, including Raman, infrared, and NMR spectroscopy, of ILs and their mixtures. This will provide valuable insights into the dissolution process of biopolymers and contribute to the improved utilization of cellulosic materials. (AU)