Phase stability of hydrogen-bonded polymer mixtures. II. Mixtures of intercomplexing polymers

Equations for the second derivative of the Gibbs energy of mixing with resp ect to composition were derived on the basis of the Barker-Guggenheim theor y of quasichemical equilibrium for mixtures of two polymers containing pola r groups and a nonpolar rest. Using equations derived, conditions for the p hase separation in mixtures of two strongly intercomplexing polymer compone nts were evaluated. The phase instability appears when the components diffe r in their polar group contents (strictly speaking, in their surface fracti ons in respective macromolecules), or due to an unfavorable interaction bet ween nonpolar groups of the components. The effect is conditioned by small affinity of polar to nonpolar groups and may be influenced by the differenc e in this affinity between both components; nevertheless, the latter factor s are not sufficient for a phase instability to occur.