Melting point depression approach: Effects of equation format on the estimated Flory-Huggins interaction parameter

Despite the widespread application of the melting point depression approach to obtain thermodynamic pa-rameters for a semicrystalline polymer-diluent mixture, a unique form of the equation is not used. Various formats employed in the literature, herein, were divided into four categories based on using a predetermined value or in situ determination of equilibrium heat of fusion (Delta H0m) for the polymeric component, as well as consideration of temperature dependency of the interaction parameter (chi). Regarding the so-called equilibrium chi of poly(3-hexylthiophene) (P3HT) in the P3HT-3-hexylthiophene (3HT) system, predicted previously, the more precise chi value (with 18% error) and its temperature dependency was obtained by in situ determination of Delta H0m and using quasi-equilibrium melting temperatures. Using a predetermined Delta H0m, however, presented an unreli-able description of the interaction parameter. Finally, a modified equation of Flory-Huggins theory was employed to estimate the chi value varying with the temperature.