Viscosities and thermodynamics of viscous flow of N-methylformamide/N-methylacetamide + polyethylene glycol 200/300/400 binary systems: Experimental and theoretical exploration

• Reports new viscosity data of NMF/NMA + PEG 200/300/400 mixtures. • Provides composition and temperature dependence of viscosity data. • Provides estimation of deviation properties of NMF/NMA + PEG 200/300/400 mixtures. • Provides information on nature of interactions and thermodyamics of viscous flow these mixtures. • Viscosity data is correlated with various empirical and semi-empirical models. The viscosities of binary mixtures of N-methylformamide (NMF)/N-methylacetamide (NMA) with polyethylene glycols (PEG 200/300/400), including those of pure liquids, have been measured across the entire range of composition at temperatures, T / K = (293.15 – 323.15) and atmospheric pressure. The experimental viscosity data have been correlated with suitable equations to represent the composition and temperature dependence of these physicochemical properties. Using the experimental data, the deviations in viscosity and excess free energy of activation of viscous flow have been calculated. The deviations in viscosity and excess free energy of activation of viscous flow were correlated by the Redlich-Kister equation. The variations of deviations in viscosity and excess free energy of activation of viscous flow with composition/temperature have been interpreted in terms of intermolecular interactions in these mixtures. The magnitude of interaction in these mixtures follows the order: NMA > NMF for each PEG and PEG 400 > PEG 300 > PEG 200 for each amide. Additionally, the thermodynamic parameters, viz. , Arrhenius activation energy, free energy, enthalpy, and entropy of activation of viscous flow have also been calculated using Arrhenius and Eyring concepts. The results have been analyzed to describe the thermodynamics of viscous flow behaviour of these systems. Further, the viscosity of the binary mixtures was estimated theoretically using various empirical/semi-empirical viscosity relations and the results were compared with the experimental data.