ON THE PECULIAR MACROMOLECULAR ORGANIZATION OF NEMATIC POLY(URETHANE-ESTER)S

The peculiar mesophase structure of a series of thermotropic poly(uret hane-ester)s is discussed. The polymers form different nematic phases, namely a nematic mesophase with cybotactic groups and a conventional nematic mesophase. The X-ray diffraction analysis suggests that two ty pes of structural arrangements, namely smectic C-like and conventional nematic structures, coexist inside the cybotactic nematic mesophases, to which different internal degrees of correlation correspond. The co rrelation length parallel to the director of the nematic mesophase ran ges from 38 to 45 Angstrom. In the cybotactic groups the correlation l engths parallel and perpendicular to the director range from 260 to 56 0 Angstrom and 130 to 270 Angstrom, respectively.