Self-Organization in Stable and Metastable Langmuir-Blodgett Films of Liquid Crystalline Porphyrins

We report an AFM imaging study of molecular self-aggregation and organization in LB layers of mesogenic porphyrin derivatives. The images were taken from molecular resolution to the mesoscopic range, as a function of deposition pressure and of elapsed time after deposition. At the molecular level, from the images we were able to determine molecular dimensions and pseudo-mesomorphic structure, which was columnar. As a function of elapsed time, such images remained stable if the deposition was performed at the pseudo-solid part of the isotherm. For deposition in the coexistence, condensed liquid stage, as a function of time the images showed remarkable molecular self-organization processes, occurring over several length scales.