Densities and Refractive Indices of Binary Mixtures of m-Cresol and Poly(ethylene glycol)s at T = 288.15–308.15 K and 96.5 kPa

In this work, the densities and refractive indices of binary mixtures of m-cresol with poly(ethylene glycol) (PEG) 200, PEG 300, and PEG 400 are measured at different temperatures (288.15, 293.15, 298.15, 303.15, and 308.15 K) and atmospheric pressures. Excess molar volume (V_m^E) and deviation in refractive index (Δn_xD) were calculated from the experimental data. Negative V_m^E values were observed for all mixtures, showing stronger heteromolecular interactions compared with homomolecular interactions. The extent of negative deviation in excess molar volume follows the order: PEG 400 > PEG 300 > PEG 200. Δn_xD values were negative for all binary mixtures across the entire composition range and temperatures studied. The Δn_xD values decrease with increasing temperature at a fixed composition for all systems. The Redlich–Kister-type polynomial equation is used to describe the excess molar volumes and deviations in refractive indices, leading to the estimation of binary coefficients and standard errors. Seven mixing rules (Arago–Biot, Dale–Gladstone, Lorentz–Lorenz, Heller, Weiner, Newton, and Eyring–John) were employed to calculate the refractive indices of the binary mixtures. The study provides insights into molecular interactions and the mixing behavior of m-cresol with different molecular weight PEGs, which is valuable for various industrial applications.