Conformations of poly(dihexylsilane) embedded in Langmuir-Blodgett multilayers of arachidic acid

Poly(dihexylsilane) (PDHS) and arachidic acid (AA) were co-spread onto a cadmium-containing water subphase and transferred onto a solid substrate as multilayers by the Langmuir-Blodgett method. The structure of these films was evaluated by means of UV-visible absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray diffractometry, and film thickness measurements. The results indicated that the PDHS ultrathin film is incorporated into a well-structured AA multilayer matrix without appreciable destruction of the layer structure. The conformational behavior of PDHS embedded within this film was evaluated by UV-visible absorption spectroscopy. The phase transition temperature of the ordered (all-trans zigzag) to the disordered (helical gauche) state on the AA monolayer at the air-water interface is lowered and the conformational state is virtually maintained in the as-deposited multilayers during storage at room temperature at least for a month. PDHS in the AA multilayer on heating showed a substantially broadened transition around 40°C, which clearly reflects a geometrical restriction effected by the AA multilayer matrix.