W. Brostow (1), K. Hibner (2), J. Walasek (1,2)

(1) Department of Materials Science and Chemistry, University of North Texas, Denton, TX 76203-5310, USA
(2) Department of Physics, Technical University of Radom, 26-600 Radom, Poland

ABSTRACT

The starting point is our previous study of influence of the internal molecular mean field of dipole-dipole interactions on local orientation and phase transitions in polymer liquid crystal (PLC) systems of longitudinal chains. Electric dipoles are created by LC mesogen moieties. Th longitudinal PLC is a macromolecule of consecutively copolymerized LC and flexible polymer sequences. We now amplify the model by inclusion of dipole-external electric field interactions. We find that the external fields can seriously codify the local orientational order of the system and affect phase transition parameters dependent on that order. In particular, the external fields induce the formation of disoriented nematic phases with negative values of the second order orientation parameter < P₂ > for LC sequences in the longitudinal PLCs while the first order parameter < P₁ > is positive. However, some rapid decreases in < P₁ > are observed at points of positive-to-negative transitions of < P₂ >; thus the LC disorientation manifests itself. The limiting case of the monomer liquid crystal (MLC) systems is included also.