Free Volume, Cohesive Energy Density, and Internal Pressure as Predictors of Polymer Miscibility

Abstract

In this paper, we illuminate and predict trends in polymer miscibility using our model understanding of pure component properties. We introduce a new metric that maps a bulk property to a theoretical characteristic parameter, viz. the percent free volume of a polymer melt as a function of the strength of its segment–segment (nonbonded) interaction energy. To this end we apply our simple Locally Correlated Lattice (LCL) model, first to characterize several dozen polymers via pressure–volume–temperature (PVT) data, and then to calculate properties that cannot be directly determined via experiment, such as percent free volume and cohesive energy density, and we rank all of the polymers in terms of these properties. We reveal strong correlations between bulk behavior and theoretical pure component character, and use those correlations to motivate a discussion of what drives polymer miscibility.