SAFT-LC: A New Equation of State for Predicting Mesophase Formation in Carbonaceous Materials

摘要

Two theories have been used to describe the formation of carbonaceous mesophase: (1) high-molecular weight (MW) pitch fractions have limited solubility in the lower MW fractions, leading to precipitation of the high-MW mesophase, and (2) the free energy of the high-MW pitch molecules is reduced by a concerted molecular orientation, resulting in the formation of a separate, liquid crystalline phase, or mesophase. These two theories are based on different chemical principles and are described by different classes of models. We propose a general model of mesophase formation that unifies these two approaches by integrating a model for non-ideal mixing with another model derived from the statistical molecular theories of the liquid crystalline state. In particular, we have combined the nonideal mixing approach of SAFT with the statistical liquid crystal theory of Luckhurst and co-workers to develop a new model capable of describing both solvent processing and mesophase formation with a single thermodynamic formulation. Our equation, which we call "SAFT-Liquid Crystal", or SAFT-LC, can not only be used to correlate existing experimental data, but has also been shown to give reasonable predictions of phase behavior for solvent-pitch systems that have yet to be measured.