Paving the Way for Understanding the Binding and Molecular Aspects of PEG 400 + Propane-1,2,3-triol (Glycerol) Binary Mixtures at Different Temperatures through Their Thermophysical, Thermodynamic, and Theoretical Properties

Abstract

The study of thermodynamic properties provides insight into the behavior of liquid mixtures. This work investigates the thermophysical and volumetric properties, as well as the excess activation of viscous flow properties of poly(ethylene glycol) 400 (PEG 400) + glycerol solutions at different compositions (x_PEG400 = 0.0–1.0, Δx_PEG400 ≈ 0.2) and temperatures (298.15–373.15 K) under atmospheric pressure (0.1 MPa). Absolute density (ρ), dynamic viscosity (η), activation energy for viscous flow (E^‡_a), and thermal expansivity (α) were determined, together with the excess molar viscous flow properties such as ΔG^‡,E_m, ΔS^‡,E_m, ΔH^‡,E_m, and excess molar volume (V^E_m). Molecular dynamics simulations were employed to obtain the density, kinematic viscosity (ν), thermal expansivity, and average hydrogen bond numbers, while intermolecular interactions were analyzed using noncovalent interaction (NCI) analysis based on the reduced density gradient. The results indicate that PEG 400 concentration and temperature affect viscosity and related thermodynamic properties, mainly associated with changes in the hydrogen bonding between PEG and glycerol. Increasing temperature weakened these interactions, leading to lower viscosities and activation energies. Theoretical results followed trends consistent with experimental observations.