Structure and thermal stability of cadmium arachidate/poly(tert-butyl methacrylate) alternating Langmuir–Blodgett film

Layer structure and thermal stability of alternating Langmuir–Blodgett (LB) films of cadmium arachidate (CdA2) and poly(tert-butyl methacrylate) (PtBMA) was investigated by X-ray reflection and in-plane diffraction study. The LB films were deposited on hydrophobically pre-treated silicon wafer surface and the polymer layers are inserted between CdA2 bilayers. Layer spacing of the alternating LB film increases linearly by 9.8 Å per PtBMA layer, which is consistent with the single layer spacing of homo-PtBMA LB film. l lattice structure of CdA2 in alternating LB films maintains its hexagonal packing structure as found in CdA2 monolayers while the multilayer CdA2 LB film is known to change its structure from hexagonal to orthorhombic lattice. Therefore, the polymer layers inserted between CdA2 bilayers in the alternating LB films effectively prevent the CdA2 film not only from the growth of defect but also from the formation of three-dimensional crystallites of CdA2. In addition, the hexagonal packing structure of CdA2 bilayer was maintained up to 90°C while the molecular area increases slightly.