Molecular thermodynamics of binary polymer solutions using modified double lattice model: Chain length dependence of primary lattice

Abstract

In a previous study we modified a double lattice model by introducing a new interaction parameter, which improved the mathematical approximation defect, and gave a new expression for the Helmholtz energy of mixing. In the model the universal constants Cβ and Cγ in the primary lattice were determined by comparing them with literature Monte Carlo simulation data, which is the only case for r1 = 1 and r2 = 100 (case I). In this study we introduce new universal constants, Cβ and Cγ, as a function of the chain length of a polymer in a solvent (case II) by comparing them with other literature simulation data for various polymer chain lengths. The proposed model is compared with polymer–solvent systems. In an upper critical solution temperature phase behavior the theoretical results of case II were improved over those of case I. However, in a lower critical solution temperature phase behavior those of case I were not very sensitive to Cβ and Cγ. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 2627–2633, 1999