where [DELTA][alpha] is anisotropy of molecular polarizability
, [mu] is the resultant dipole moment of the molecule, N is the molecular number density, [DELTA][alpha] is dielectric anisotropy, F is parameter depending on reaction field factor, and [beta] is the angle between the molecular axis and the direction of the off axis.
In solutions and melts, where the stresses originate from entropy elasticity, this coefficient scales with the anisotropy of the molecular polarizability of the polymer chain, [DELTA][alpha] (14, 15), as expressed in Eq 2.
For the stress-optical behavior in the glass state at small strains the relation to the molecular polarizability is less well understood, although a correlation to [DELTA][alpha] has been suggested (17, 18).
FB-PC also has a negative molecular polarizability very much like SBI-PC.