STRUCTURE AND MORPHOLOGY OF LANGMUIR-BLODGETT-FILMS OF ROD-LIKE POLY(PHTHALOCYANINATO GERMOXANE)S, STUDIED BY TRANSMISSION ELECTRON-MICROSCOPY

The domain structures and molecular orientation in Langmuir-Blodgett m ono-, double and multilayers of rod-like poly(pthalocyaninato germoxan e)s with dodecyloxycarbonyl side-chains deposited onto a carbon film s ubstrate are directly visualized using electron diffraction (ED), as w ell as bright-field (BF) and dark-field (DF) imaging. The ED patterns show an oriented intramolecular spacing of 0.37 nm from the axially st acked phthalocyaninato rings, aligned along the dipping direction and an orthogonally oriented intermolecular spacing of 3.4 nm, arising fro m parallel packing of rod-like molecules parallel to the layer plane. In addition, arched (hkO)-type reflections arise from about 40% of the film area of a single monolayer, indicating an end-on orientation of the rod-like molecules relative to the layer plane. In multilayer film s, a two-dimensional hexagonal phase and a less ordered layer state wi th no registration between the molecules in adjacent layers coexist, a nd the portion of molecules oriented preferentially normal to the laye r significantly decreases. The BF images of the monolayers and double layers show a mosaic-like structure, with darker band-like regions abo ut 50 nm in size surrounding brighter mosaic pieces about 300 nm in si ze. The DF images confirm that the darker regions in the BF image main ly arise as a result of scattering from the 0.37 nm reflection, indica ting that the rod-like molecules are oriented parallel to the layer pl ane. High resolution electron microscopy images taken from the monolay er films show patches of parallel fringes, directly visualizing the la teral 3.4 nm packing of the rods. The fringe regions exhibit a broad o rientational distribution about the dipping direction.