Langmuir-Blodgett mixed films of titanyl(IV) pthalocyanine and arachidic acid.: Molecular orientation and film structure

Langmuir and Langmuir-Blodgett (LB) films of neat titanyl(IV) plithalocyanine (TiOPc) and mixed (Tiopc)-arachidic acid (AA) films were studied. The surface pressure-area isotherms ( T-A) were recorded, and an unusual expansion of the surface area per molecule was detected for mixed TiOPc-AA Langmuir monolayers. The expansion is attributed to the TiOPc molecular orientation in the neat films being different from that in the mixed films with arachidic acid. The molecular orientation in LB films was monitored using reflection-absorption infrared spectroscopy (RAIRS). It was found that the TiOPc molecules are tilted with respect to the substrate in the neat film, changing to a preferential face-on orientation in the TiOPc-AA mixed films. Complementary information about molecular organization and film structure was obtained using UV-visible absorption and micro-Raman imaging.