Miscibility of poly (methyl acrylate) and poly (vinyl acetate): incompatibility in solution and thermodynamic characterization by inverse gas chromatography

Abstract

The miscibility of poly (methyl acrytateJ and poIy(vinyl acetate) has been studied. Glass transition temperature measurements indicated that the two polymers are miscible at all compositions. The incompatibility of the two polymers in solution with certain solvents (component l) has been examined in light of the IΔ_χI theory of Patterson et el. Determination of χ_Li values by the viscometric method using dilute polymer solutions showed that IΔ_χI values are too small to enable the tbeory to predict a phase separation. On the other hand, IΔ_χI values large enough to effect a phase separation obtain when solutions infinitely dilute with respect to the solvent molecules were used for the determination of χ_Li values by the inverse gas chromatographic (lGC) method, This calls for taking into account in the theory the composition dependence of χ_Li . Measurement. of thermodynamic interaction parameters by IGC further revealed that miscibility in the binary polymer- polymer mixture is not causod by specific interactions and that there it a lack of "complementary dissimilarity" between the molecules of the two polymers. The LCST's of the polymer blends are probably situated at temperatures much higher than the degradation temperatures of the poJymers and could not be determined. Also, no strong dependence of miscibility on molecular weights of the polymers was observed. These results are in agreement with the view that the exchange interectlon energy is positive but small, as must be the free volume contribution to the free energy of mixing.