Zhang Yumei

Effect of dimethylsulfoxide on the viscoelastic properties and sol–gel transition of cellulose/ionic liquid solutions

Viscoelastic properties of cellulose solutions with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) and dimethylsulfoxide (DMSO) as solvents were studied by rheological experiments. From the results of rheological behaviors, the non-monotonous decrease of viscosity with DMSO content was observed. When the content of DMSO in [BMIM]Cl/DMSO is lower than 5 wt% in [BMIM]Cl/DMSO, the viscosity and gelation temperature (Tgel) decreased with the increase of DMSO. However, the values of viscosity and Tgel showed a nonlinear change with the further increase of DMSO. It could be understood that DMSO acted as the diluent when the content of DMSO is below 5 wt%. The local micro-aggregation or micro-phase separation of cellulose could happen when the content of DMSO further increased due to the weak action between cellulose and DMSO.

Rheological behavior of polyarylsulfone 1-butyl-3-methylimidazolium chloride solutions

Polyarylsufone polymers are engineering thermoplastics that can only be dissolved in polar solvents. We found that polyarylsufone has good solubility in ionic liquid (IL) with IL being a new kind of green solvent; thus, ILs are potential substitutes for conventional molecular solvents. However, the thermodynamics in ionic liquids are different then those in conventional solvents, so ILs as solvents have attracted enormous attention recently. Rheological behavior is an important factor in polymer material processing. The rheological behavior of polyarylsulfone (PASF) in both N, N,‐dimethylacetamide (DMAc) and ionic liquid 1‐butyl‐3‐methylimidazolium chloride [(Bmim) Cl] were studied in this paper as a function of concentration for concentrated solutions. It is interesting that the rheological behavior of the PASF/(Bmim) Cl solution is very different from that of PASF/DMAc solutions. In DMAc, as concentration increases viscosity increases, while the rheological behavior of the PASF/(Bmim) Cl solution exhibits a maximum in the viscosity‐concentration plots.

Physical properties and solubility parameters of 1-ethyl-3-methylimidazolium based ionic liquids/DMSO mixtures at 298.15 K

Densities, refractive indices, conductivities and viscosities of binary mixtures of 1-ethyl-3-methylimidazolium-based ionic liquids (ILs) with dimethyl sulfoxide at 298.15 K are reported. Excess molar volumes have been calculated from experimental data and were fitted with Redlich–Kister equation. The density and refractive index were found to increase with increasing concentration in all cases except [EMIM]COOH. The free mobility of ions has found to enhance conductivity and decrease viscosity to varying extent in all mixtures being studied. It has been observed that solubility parameters, dielectric constants and nature of anions of ILs being used play a vital role in determining the subsequent characteristics. As DMSO has high dielectric constant therefore, it was able to form interactions with most of ILs except with [EMIM]COOH due to anomalous nature of anion.