APPLICATION OF EQUATION-OF-STATE THEORY TO RANDOM COPOLYMER SYSTEMS .1. COPOLYMER SOLUTIONS IN SOLVENT

Flory's equation-of-state theory with modified combining rules was extended to random copolymer systems. In this extended theory, the characteristic parameters and the intermolecular parameters (the exchange enthalpy parameter and the parameter characterizing the deviation from additivity of the external degrees of freedom) for copolymers are obtained from those for the copolymer components by using the combining rules for the copolymer. The theory was applied to poly(ethylene-co-vinyl acetate) (EtVAc) and poly(vinylacetate-co-vinyl chloride) (VAcVC) solutions in tetrahydrofuran (THF). For this purpose, the interaction parameter, χ, heats of mixing at infinite dilution, and excess volumes for these solutions were measured. The copolymer composition dependence of χ at infinite dilution for the EtVAc solutions showed a U-shaped curve. In application of the theory to these systems, the characteristic parameters for the copolymer components were evaluated from the P-V-T data for the homopolymers corresponding to the copolymer components, and the intersegmental parameters between the copolymer components were determined from the thermodynamic data for the homopolymer solutions and for the copolymer solution with a given copolymer composition. The theoretical calculations were performed over various copolymer compositions by using the parameters thus determined. In consequence, the theory gave satisfactory agreement with the experimental results for the dependence of the interaction parameter, χ, on the copolymer composition. © 1990, American Chemical Society. All rights reserved.