Novel solvents in cellulose chemistry: synthesis, properties, and application of quaternaryammonium electrolytes for dissolution, regeneration, and derivatization of cellulose

Abstract

Processing of cellulose, the most abundant renewable terrestrial biopolymer, is still connected with some limitations. In particular the dissolution of this polysaccharide is not fully understood. Consequently, the available commercial products are produced by heterogeneous processes (solid cellulose/liquid bath). This makes the fabrication of speciality products difficult since tailored reproducible properties are required. The growing interest in sustainable and green technologies increased the demand to develop new, more efficient cellulose solvents to replace the existing ones. In this proposal, an approach to a new class of cellulose solvents based on quaternary ammonium electrolytes (QAE) dissolved in molecular solvents, MSs, will be investigated. Cellulose dissolution in these systems is physical, i.e., without formation of covalent polymer-solvent bonds. Thus, a series of QAE will be synthesized, dissolved in various MSs, and their efficiency as cellulose solvents evaluated. Additionally, the detailed physicochemical characterization of the obtained mixtures, and cellulose solutions therein will contribute to a better understanding of cellulose-solvent interactions. This may define threshold values for various parameters of the solvent (e.g., its empirical polarity and basicity) to predict dissolution of cellulose. These parameters will be determined by use of solvatochromic indicators. The best solvent system(s) will be used as medium for dissolution of microcrystalline and fibrous cellulose, regeneration, and its controlled acylation under homogeneous reaction conditions in order to obtain mixed esters of carboxylic acids with new properties. (AU)