Applying the Langmuir-Blodgett technique to a well defined model detergentsystem

The Langmuir-Blodgett technique is used to obtain a well defined model dete rgent system. Spreading monolayers of arachidic acid as a model organic con taminant are transferred onto glass plates untreated and treated with two s ilane coupling agents, gamma -aminopropyltriethoxysilane (APTES) and methyl triethoxysilane (MTES). Brewster angle microscopic images show that the LB films of arachidic acid are uniformly deposited on the substrate. Glass pla tes with the LB films are ultrasonically washed in various aqueous solution s, and the detergency is evaluated from the change in FTIR spectra of the s ubstrate due to washing. The efficiency of detergency decreases as a result of the silanization of glass, especially for the APTES treated glass. The wettability and the surface charge of the substrate play important roles in the detergency, suggesting that the LB films of arachidic acid are removed directly from the substrate. Removal of LB films from the APTES-treated gl ass increases with increasing surfactant or ethanol concentration, and the removal rate strongly depends on temperature. As a removal technique withou t washing liquids, exposure of the substrates with LB films to 172 nm ultra violet light is also attempted.