Polymer Incompatibility Caused by Different Molecular Architectures: Modeling via Chain Connectivity and Conformational Relaxation

摘要

The calculation of phase diagrams for blends of linear and branched polymers made up of identical monomeric units is modeled using an approach that subdivides the mixing process into two steps: i) contact formation between the different components, keeping their chain conformations and the volume of the system constant; and, ii) relaxation of the macromolecules into their equilibrium state by molecular rearrangements. It is assumed that step (ii) causes shape-induced polymer incompatibility and that the degree of branching can be quantified in terms of the volumes the isolated coils of the branched polymer occupy in relation to the volume the linear product with the same molecular weight occupies. Under these premises, it is possible to work out how the critical conditions depend on the molar masses of the components and on the degree of branching of the non-linear polymer by means of only one system-specific parameter, measuring the effects of conformational relaxation. Detailed phase diagrams show how the binodal and spinodal conditions reflect the conformational variability of the blend components.