| Current studies take in account determination of physical properties of binary mixtures of different ILs with different organic solvents at room temperature. The organic solvents being used exhibit diverse extent of polarity or dielectric constants and solubility values leading to varying miscibility with IL. For1-butyl-3-methylimidazolium chloride([BMIM]Cl)/organic solvent systems, the density increases by increasing concentration of IL for all systems except [BMIM]Cl/DMSO (dimthylsulfoxide). The excess molar volumes for other systems (except [BMIM]Cl/DMSO) were found to have negative values. The negative values clearly indicate the existence of interactions and certain associations among the molecules of IL and organic solvents. However,[BMIM]Cl/DMSO system has shown positive values and clearly indicate the existence of hydrogen bonding as a source of intermolecular interactions. Refractive index of [BMIM]Cl with acetone, acetonitrile, DMSO and ethanol exhibits same behavior i.e. increase with increasing concentration of IL. On the contrary, mixture of acetone/IL has shown immiscibility with the IL at certain concentrations due to its lowest dielectric constant among all the solvents being used. Apart from these exceptional cases, acetonitrile and ethanol have illustrated moderate miscibility. In the next part, physical properties of [EMIM]-based ILs were studied in the presence of ethanol or DMSO. Except [EMIM]COOH, all mixtures showed same behavior for density, refractive index, conductivity and viscosity measurements. For [EMIM]COOH, refractive index tends to decrease with increasing concentration which is quite contradictory behavior for its mixture with DMSO. This behavior was suggested to be related to complete inability of ILs molecules to form any type of association and aggregation with DMSO molecules. Different organic solvent and ILs showed distinct extent of interactions which clearly affected the resultant properties. It was evaluated that the molar mass and hydrogen bonding ability of anion, solubility parameters and dielectric constants of solvents being used play an important role in determining the extent of solute-solvent interactions within these mixtures.For further studies, ternary mixture involving cellulose/IL/organic solvent has been investigated by rheology. DMSO has been selected to study the behavior of dissolved cellulose because of its unique properties as discussed. Viscoelastic properties of cellulose dissolved in [BMIM]Cl)with co-solvent DMSO were studied in the concentration range of DMSO from1-10%. The sol-gel transition process was discussed according to the Winter and Chambon’s theory. The influence of DMSO concentration on the gelation temperature was found to be similar with that on the zero shear viscosity. It shows that cellulose aggregations exist in the solution of10%DMSO concentration, resulting in the low mobility of chains and occurrence of gel network structure at higher temperature.In order to further elaborate our concept and objective of research, the ternary solution of8wt%cellulose in3wt%DMSO/[BMIM]Cl was spun into fibers by dry jet wet spinning. It has been discovered that DMSO was able to clearly interact with the polymer as well as the IL and hence led to improvements of certain resultant properties. However, a DMSO/IL solvent was unable to enhance the elongation of these fibers but granted them with greater strength. This system was found to be more effective for the dissolution as well as regeneration of cellulose as is quite evident by FT-IR and XRD results. However, different spinning conditions showed different trends.It has been summarized that cellulose/[BMIM]Cl/DMSO solution’s rheological behavior, tests for a dry-jet wet spun fibers suggested that when the content of DMSO is3wt%does not affect the spinnability and still the spinning temperature can be reduced to80℃. |
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