STRUCTURAL INVESTIGATION OF PHTHALOCYANINATOPOLY(SILOXANE) LANGMUIR-BLODGETT-FILMS BY X-RAY-DIFFRACTION

The structure of Langmuir-Blodgett (LB) films of a rigid rod phthalocyanatopoly(siloxane) substituted by alkoxy side chains has been investigated by X-ray diffraction using thin silicon wafers as a substrate for deposition. Freshly prepared samples do not possess a truely periodic multilayer structure. The polymer backbones lie flat in the substrate plane and are preferentially oriented along the dipping direction. Each macromolecule is surrounded by parallel adjacent rods and a first-neighbor distance is found in every direction. This structure recalls the local organization of a nematic liquid crystal. Short annealing of the as-deposited films leads to a highly oriented hexagonally dense packing as of cylinders. The alignment of the backbones along the dipping direction becomes nearly perfect and the most densely packed plane is oriented in the substrate plane. A helical order within the macromolecules of the annealed samples is suspected from extra reflections appearing in the diffraction pattern.