Langmuir-Blodgett films of metal complexes of 4-(10,12-pentacosadiynamidomethyl)pyridine: A structural investigation

Complex formation between 4-(10,12-pentacosadiynamidomethyl)pyridine and metal ions in the subphase results in stable Langmuir monolayers up to surface pressures of 35 mN m(-1). Electron microscopy pictures show a flat monomer monolayer before polymerization and a polymer monolayer exhibiting a more striated structure after polymerization. Multilayers of the amphiphile can only be built up after complexation with metal ions. X-ray photoelectron spectroscopy (XPS) measurements definitely confirm the presence of metal ions in the multilayers, and the molar ratio between metal and amphiphile is derived from the spectra. These multilayers are further characterized by means of small-angle X-ray reflection measurements and Fourier transform infrared (FT-IR) spectroscopy, which show that the amphiphile has a large tilt angle (a) with respect to the surface normal. The multilayers are polymerized by means of UV irradiation, and UV-vis spectroscopy is used to study the polymerization process. The structural changes during polymerization are deduced from small-angle X-ray reflection measurements and FT-IR spectroscopy. In all cases, the bilayer spacing decreases during the polymerization process, whereas in some cases the regular plane of the all-trans conformation of the alkyl chains is converted to an irregular one containing gauche conformations. For multilayers built up from a CuCl2-containing subphase, the whole distinct layer structure is destroyed during the polymerization process.