The effects of branching and deuterium labeling on blend miscibility

Abstract

The individual and combined effects of 4-arm star branching and deuterium labeling on polystyrene (PS) influence its compatibility in upper critical solution temperature (UCST) and lower critical solution temperature (LCST) mixtures. In this article, we use our Locally Correlated Lattice (LCL) model to characterize a set of PS samples in their pure states in order to predict miscibility trends for blends of PS with poly(vinyl methyl ether) (PVME) (LCST-type mixtures) and isotopic variants of PS (UCST-type mixtures). We find that 4-arm star branching and/or deuterium labeling can shift the pure component properties of PS, such as its percent free volume or cohesive energy density, which affects how the properties of PS ‘match’ those of the other mixture component. In another section of this article, we turn to modeling the blends, themselves, and provide fundamental thermodynamic insight about the PS/PVME mixtures by calculating the relative enthalpic and entropic contributions to the free energies of mixing. We observe trends in the values of the entropies and enthalpies of mixing for the PS/PVME blends that qualitatively match our pure component properties analysis of the pure PS samples.