MOLECULAR ORDER WITHIN LANGMUIR-BLODGETT-FILMS OF 2 AMPHIPHILIC OCTASUBSTITUTED PHTHALOCYANINES STUDIED BY ATOMIC-FORCE MICROSCOPY

Y-type Langmuir-Blodgett films of the octasubstituted amphiphilic phth alocyanines 1 and 2 deposited onto hydrophobic glass have been investi gated by atomic force microscopy(AFM). The technique has been used to measure the thicknesses of one, two, and three bilayer films, and the results show that each bilayer is of the same thickness. This characte ristic thickness is the same as the repeat spacing measured using low- angle X-ray diffraction methods on thicker samples, and thus we demons trate that the order of the molecules in the monolayers after several cycles of deposition remains constant. We have detected considerable d ifferences with respect to the consistency of the films of 1 and 2 and their resistance to the pressure exerted by the AFM tip during the sc anning process required to obtain the images. Films of 1 are more robu st and we have observed the columnar arrangement of the molecules at t he surfaces of one, two, and three bilayers. However, under the same i maging conditions it was not possible to observe molecular order befor e perturbing the surface of the films formed by 2. The lateral extent of the ordered regions at the surfaces of the films of 1 covers areas of at least 10 mu m(2). There is very clear evidence that there is a p redominant alignment. Inspection of 82 images taken of different regio ns of the film indicates that ca. 83% show columns whose axes are alig ned to within +/-30 degrees of the dipping direction.