Solvation in cellulose-LiCl-DMAc solutions

The development of a new, more environmentally compatible process for making rayon, compared with the old viscose process, was accompanied by a search for alternative solvents for cellulose, and has attracted a great deal of academic as well as industrial interest in recent years. Among others, the system N,N-dimethylacetamide with lithium chloride (LiCl-DMAc) has turned out to be a promising candidate. However, a process based on this solvent system has not been established, as yet, since the costs for recovery of the solvent components, especially LiCl, are too high. Nevertheless, a challenging problem is to understand the solution state of cellulose and the dissolution mechanism in this and related solvent systems. This paper reviews the different ideas on both the structure of solvent systems and the dissolution of cellulose that have been published in recent years. Especially, it focuses on ligand exchange in solvated LiCl ion pairs, which leads to solvation of the hydroxyl groups of cellulose.