INPLANE ORIENTATION OF PYRROLE DERIVATIVES BEARING A SIDE-ON LIQUID-CRYSTAL GROUP

Pyrrole derivatives bearing a side-on liquid crystal group form stable Langmuir films at the gas-water interface. The compression isotherm o f those unusual compounds exhibits a plateau which corresponds to a ph ase transition as demonstrated by Brewster angle microscopy and X-ray reflectivity measurements. Transfer of the monolayers onto solid subst rate leads to Langmuir-Blodgett films in which in-plane orientation is found for the mesogenic parts. The liquid crystal groups are found to be lying more or less parallel to the dipping direction. This orienta tion is then perpendicular to that of disk-like molecules already desc ribed for their in-plane orientation. Finally, the effect of the exact molecular structure on the order parameter describing the orientation al anisotropy of these pyrrole derivatives is discussed. (C) 1998 Else vier Science S.A. All rights reserved.