Preparation and characterization of ultrathin layers of substituted oligo- and poly(p-phenylene)s and mixed layers with octadecanethiol on gold and copper

Substituted poly(p-phenylene)s were adsorbed from solution onto gold and copper and oligo(p-phenylene)s onto gold. The layers were investigated with IR spectroscopy at grazing incidence reflection, XPS, NEXAFS, ToF-SIMS, surface profilometry, AFM, SEM, optical microscopy, ellipsometry, and contact angle measurements to examine their formation and structure. The structure and the properties of the investigated layers depend not only on the chemical structure of the polymer but also on the type of substrate. On gold, the polymers form layers of 15-25 angstroms in thickness and the oligomers of ca. 5 angstroms in thickness. On copper, `thick' layers of up to 900 angstroms were also observed. The oligomers have a lower affinity to gold than the polymers. Mixed octadecanethiol-polymer layers were prepared by immersion of polymer-coated substrates in an octadecanethiol solution or by exposure of self-assembled monolayers of octadecanethiol to polymer solutions. The structure of the mixed layers depends on the sequence of the exposure of the two components and on the chemical structure of the polymer. In the mixed layers, structures that protrude above the surroundings were frequently detected at the surface.