  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.
