Self-assembled layers of substituted poly(p-phenylene)s on gold and copper investigated by soft X-ray spectroscopy

Near edge X-ray absorption fine structure spectroscopy (NEXAFS) was used to investigate the adsorption of self-assembled substituted poly(p-phenylene)s on gold and copper surfaces from solution. While on gold only films with thicknesses in the monolayer range were found, on copper ''thick'' layers were also detected. The properties of the films depend on the chemical structure of the molecules and the immersion time of the substrate in solution. The determined mean tilt angles of the phenyl rings in the rigid polymer backbone and side chains indicate that the influence of the substrate on the orientation is strongest for thin films on gold and copper and diminishes for thick films on copper., Interaction of polymers with the substrate was found to occur via the pi*-system of the phenyl rings. In the case of ''thick'' layers, the distinction between adsorbate and substrate becomes ill-defined, since there appears to be strong evidence for the presence of organometallic complexes in a long-ranging graded interphase.