Mixing Thermodynamics and Flory-Huggins Interaction Parameterof Polyethylene Oxide/Polyethylene Oligomeric Blends fromKirkwood-BuffTheory and Molecular Simulations br

In this study, we conduct a full thermodynamicanalysis of polyethylene oxide/polyethylene oligomeric blends,building on the methodology introduced by Petris et al. [J. Phys.Chem. B,2019,123, 247-57], using which we contribute to theinterpretation of large-scale molecular dynamics (MD) oligomericblend simulations in the light of Kirkwood-Buff(KB) theory,featuring a composition-dependent estimation of the Flory-Huggins interaction parameter. The KB integrals are calculatedfromNpTMD trajectories using the particlefluctuation method.The component activity coefficients, the excess Gibbs energy ofmixing, the volume, enthalpy, and entropy of mixing are extracted as functions of the mole fraction. The Flory-Huggins interactionparameter chi is estimated by interpreting the Gibbs energy of mixing in the framework of Flory-Huggins theory, and its dependenceon composition is explored. A structural analysis of the studied oligomeric blends is performed to obtain the mean squared radius ofgyration, the molecular pair distribution functions, and the dihedral angle distributions of the two components and is used tointerpret the predicted thermodynamic properties. All the results are compared against experimental measurements and previoussimulations, where available, and the agreement is found to be very good, validating our proposed methodology