Molecular Interactions Studies of Dimethyl Sulfoxide, <i>N</i>-Methyl-2-pyrrolidone, and Water Binary Mixtures at Varying Temperatures: Volumetric and Spectroscopic Investigations

Thermophysical properties are crucial for various industrial applications, process designs, and modeling as they provide insight into intermolecular interactions. In this work, the binary mixtures of polar aprotic solvents dimethyl sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP) with a polar protic solvent, water, has been investigated to assess intermolecular interactions and structural behavior. Density (ρ), molar volume (Vm), and coefficient of thermal expansion (αP) along with excess coefficient of thermal expansion (αPE), excess molar volume (VmE), and FTIR analysis of binary mixtures were evaluated at various temperatures (293.15–318.15 K). The result reveals that a strong hydrogen-bonding network of water molecules is broken down by DMSO and NMP molecules between 0.3 and 0.4 mole fractions. The new network of hydrogen bonding formed within DMSO + water and NMP + water is strong and hetero-associated, expressed by the negative value of VmE. The packing factor in NMP + water affects VmE showing more molecular interactions than DMSO + water. The DMSO + NMP mixture reveals positive VmE values, indicating the self-association of polar solvents.