This study presents a comprehensive numerical analysis of the binodal and spinodal phase behavior of a high-pressure binary mixture of polyethylene glycol (PEG) and supercritical carbon dioxide. Understanding these phase boundaries is crucial for applications involving polymer processing and separation technologies. PC SAFT equation of state has been implemented to delineate the binodal curve, indicating the equilibrium coexistence of two phases, and the spinodal curve, marking the limit of metastability where phase separation occurs spontaneously. The simulations reveal the critical conditions under which the PEG–supercritical CO₂ system transitions between homogeneous and heterogeneous phases. Furthermore, the nucleation mechanisms have also been investigated, triggered by temperature swings, elucidating the pathways of both homogeneous and heterogeneous nucleation within the metastable region. Nucleation rates and subsequent crystal growth kinetics have also been quantified by integrating classical nucleation theory with the phase behavior analysis. Finally the influence of the factors such as supersaturation levels, temperature, and pressure on the nucleation rate and crystal growth has been examined through a sensitivity study to find the most influential parameter.
