![]() ![]() ![]() They often possess high thermal and chemical stability, although the cellulose-solvating structures tend to be the least stable (King et al. ILs are salts, typically composed of an organic cation and an inorganic or organic counter anion. ![]() 2003) Ionic liquids (ILs) were first demonstrated to dissolve cellulose by Swatloski et al. Therefore basic-amphiphilic solvents, such as ILs, have been successful in the dissolution of cellulose (Himmel et al. Cellulose has a very low solubility in water and other conventional organic solvents because of the extensive H-bonding network and amphiphilicity of the rigid cellulose chains. In many of these applications, pre-dissolution of cellulose, to form close to isotropic solutions, is assumed. This is already commercialized using NMMO-water mixtures, in the form of the Lyocell process (Fink et al. More modern applications, involving dissolution and regeneration, include regeneration and spinning into textile fibers. Regular micro-sized particles regenerated from a cellulose-OES mixture of tetrabutylphosphonium acetate:DMSO (70:30 w/w) upon coolingĬellulose is widely used in various industries and material processing, although it has not reached the same scale of use, compared to petrochemical-based polymers, as it lacks a melting point and does not dissolve in any non-derivatizing molecular solvents. The influence of the experimental conditions, cellulose concentration and the effect of time on regeneration of cellulose in the form of preferential gel or particles is discussed. The regeneration process is a consequence of multi-parameter interdependence, where the polymer characteristics, OES composition, temperature, cooling rate and time all play their roles. The particles are obtained below the phase-separation temperature as a result of controlled multi-molecular association. While this phenomenon has been reported for other IL and NMMO-based systems, the mechanisms and phase-behavior have not been well defined. This observed UCST-like behavior of these systems allows for the controlled regeneration of cellulose into colloidal dispersions of spherical microscale particles (spherulites), with highly ordered shape and size. This phenomenon much resembles the upper-critical solution temperature (UCST) type thermodynamic transition. Cellulose can be first dissolved in these OESs at 120 ☌ and then regenerated, upon cooling, leading to micro and macro phase-separation. Herein we use OESs consisting of two tetraalkylphosphonium acetate ILs and dimethyl sulfoxide or γ-valerolactone, as co-solvents. In some cases, organic electrolyte solutions (OESs), that are binary mixtures of an ionic liquid and a polar aprotic co-solvent, can show even better technical dissolution capacities for cellulose than the pure ILs. More recently, ionic liquids (ILs) have been used for cellulose dissolution and regeneration, for example, in the development of textile fiber spinning processes. Cellulose is an historical polymer, for which its processing possibilities have been limited by the absence of a melting point and insolubility in all non-derivatizing molecular solvents. ![]()
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