PVT Relations for Polymeric Liquids

Numerous equations of state for polymer liquids have been developed. These equations provide valuable thermodynamic information that can be used to predict properties of polymer blends and polymer solutions. The predictions of phase behavior of polymer blends vary considerably from one equation of state to another. EOS theories for polymer liquids can be roughly grouped into three kinds  

The three categories differ in how they represent the compressibility and expansion of the polymer systems under scrutiny. Volumetric changes are restricted to a change in cell volume in cell models. Lattice vacancies are allowed in lattice-fluid theory, and the cell volume is assumed constant. Cell expansion and lattice vacancies are allowed by hole models. The models also differ on the lattice type, such as a face-centered cubic, orthorhombic, hexagonal, and also in their selection of interpolymer/interoligomer potential such as Lennard-Jones potential, hard-sphere, or square-well. 

Six of the commonly used EOS for polymers were reviewed by Rodgers [9]. The six EOS are discussed in the following sections. 

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