RIS theory of the Kerr effect in strong electric field for long flexible polymers with induced dipole moment

Abstract

The theory of the Kerr effect in a strong electric field for long polymer chains with an induced dipole moment is presented based on the rotational-isomeric states (RIS) model on a tetrahedral lattice. The body of mathematics used earlier for chains with a permanent dipole moment is adapted for chains with an induced moment. Chains having induced longitudinal dipole moments and chains with permanent transverse dipole moments (type B chains) are oriented differently in the external field. Nevertheless, these chains have similar conformational properties. In a strong external electric field, conformational properties of chains possessing induced dipole moments are similar to those of type B chains. However, the total number of “kinks” and “folds” for chains with induced longitudinal dipole moments is larger than for type B chains assuming the same quadrupole order parameter S per monomer unit. This result is consistent with a larger effective segment in type B chains as compared to chains with induced longitudinal dipole moments. Orientation in the strong external field of chains with different types of polarity in a first approximation may be represented as orientation of a simple freely jointed chain with the effective segment equal to the average length of a regular trans sequence.