Molecular-Level Interactions in Binary Mixtures of 1-Ethyl-3-methylimidazolium Ethylsulfate and Propane-1,2-diol: The Interplay between Intermolecular and Intramolecular Hydrogen Bonding

In this study, volumetric properties of an ionic liquid, 1-ethyl-3-methylimidazolium ethylsulfate ([C2mim]C2H5SO4), propane-1,2-diol, and their binary mixtures were studied by measurements of density and viscosity. The excess molar volume (VmE), dynamic viscosity deviation (Δη), and excess molar Gibbs free energy of activation for viscous flow (ΔGm*) were calculated and fitted with the Redlich-Kister (RK) type polynomial equation. The results suggested that intermolecular interactions are weaker in the mixture compared to the pure components and the interactions decrease with increasing mole fraction of [C2mim]C2H5SO4. The thermodynamic activation parameters were also calculated from the Eyring equation, and their variations with mole fraction of [C2mim]C2H5SO4 were correlated to the molecular-level interactions. The near-infrared (NIR) spectroscopic measurements were carried out in the temperature range from 293.15 to 333.15 K. The raw NIR data were analyzed further by two-dimensional correlation spectroscopy and principal component analysis. When [C2mim]C2H5SO4 was introduced to the propane-1,2-diol system, the stronger intermolecular hydrogen bonds were destroyed. Propane-1,2-diol and [C2mim]C2H5SO4 produce some weaker hydrogen bonds, but the effect of breaking hydrogen bonds predominates. On the basis of volumetric and NIR spectroscopic investigations, molecular-level interactions are predicted. The interplay between intermolecular and intramolecular hydrogen bonding decides unique molecular-level interactions and dictates enhanced thermodynamic properties of the binary mixtures to make them tunable for a multitude of applications.

Characteristics of a PVDF-Tin Dioxide Membrane Assisted by Electric Field Treatment

Polymeric membranes have good properties for filtering water. In this paper, a membrane made from polyvinylidene fluoride (PVDF) polymer with 15 wt%, 17.5 wt%, and 20 wt% polymer content, with the addition of 1 wt% of tin dioxide with electric field treatment, is presented. The electric field used was DC 15,000 V. The membrane was tested to determine its characteristics and properties. The physical properties were examined with a scanning electron microscope, and the mechanical properties of the membrane were tested by tensile testing. The maximum tensile stress was obtained at 0.746 MPa, and the minimum tensile stress was obtained at 0.487 MPa. Microscopic examination of the membrane's surface identified the shape, the structure of the fibers formed, and the amount of agglomeration. The flow rate, membrane flux, and normalized water permeability (NWP) were tested, using the water treatment performance test to measure the membrane's filtering ability.