On the Thermodynamic Properties of Solutions of Polar Polymers. Theory

Abstract

In this paper we present a simple analysis of the thermodynamic properties of solutions of polar polymers. It is found that: (a) In the dilute solution regime, a cluster analysis identical with that used in the theory of solutions of nonpolar polymers can be developed, but with the thermodynamic parameter z now dependent on the dipole moment, dielectric constant, etc. (b) In the concentrated solution regime, a continuum theory can be developed based on the assumption of uniform mixing of polymer chains and the use of cavity field and reaction field arguments. (c) For dilute solutions of a polar polymer in a nonpolar solvent, or a nonpolarizable polar polymer in a polar solvent, the system is equivalent to an ordinary nonpolar polymer-poor solvent system. (d) It is generally true that the solvent becomes poorer as the dipole moment and/or polarizability of the segment are increased. Also, the solvent becomes better as its dielectric constant increases. (e) In the case of concentrated solutions of a polar polymer in a nonpolar solvent, the polar contribution to the Flory-Huggins free-energy parameter, χp, decreases with increasing concentration. (f) In the case of concentrated solutions of a nonpolar polymer in a polar solvent, χp increases with increasing concentration. (g) The dilute solution theory and concentrated solution theory predict the same functional form for χp in the limit of zero polymer concentration, but the numerical coefficients differ. (h) The results of extensive digital computer calculations are presented in terms of the predicted concentration dependence of χp with varying properties of both polymer and solvent. Agreement between theory and experiment is examined in detail in the following paper.