Theory of electric birefringence in a strong field for a long flexible polymer chain: Tetrahedral lattice model

The Kerr effect for a long polar polymer chain in a strong electric field i s studied using the rotational-isomeric-state model on a tetrahedral lattic e. A polymer chain containing only a longitudinal component of the dipole m oment has been considered. In such chains the Kerr effect is the largest. T he field dependence of conformational properties and of orientational chara cteristics has been calculated. The overall chain behavior in a strong elec tric field can be treated as a superposition of two effects: (1) an elongat ion of the "effective" rigid element of the chain (the rigid elements can b e considered as;the trans sequences in the chain between gauche isomers); ( 2) an orientation of the "effective" segment like that in the freely jointe d chain.