Enhanced phase segregation induced by dipolar interactions in polymer blends

TL;DR

This paper develops a generalized theory to analyze how dipolar interactions influence phase separation, interfacial tension, and stability in polymer blends with dipolar backbone monomers, extending classical models.

Contribution

It introduces a new theoretical framework incorporating dipolar effects into phase diagrams and interfacial properties of polymer blends, including corrections to Flory-Huggins theory.

Findings

Mismatch in dipole moments destabilizes homogeneous phases.

Interfacial tension increases with dipole moment mismatch.

Density profiles and interfacial tensions are characterized for different interface types.

Abstract

We present a generalized theory for studying phase separation in blends of polymers containing dipoles on their backbone. The theory is used to construct co-existence curves and to study the effects of dipolar interactions on interfacial tension for a planar interface between the coexisting phases. We show that a mismatch in monomeric dipole moments, or equivalently a mismatch in the dielectric constant of the pure components, leads to destabilization of the homogeneous phase. Corrections to the Flory-Huggins phase diagram are predicted using the theory. Furthermore, we show that the interfacial tension increases with an increase in the mismatch of the dipole moments of the components. Density profiles and interfacial tensions are constructed for diffuse and sharp polymer-polymer interfaces by extending the formalisms of Cahn-Hilliard and Helfand-Tagami-Sapse, respectively.