The opportunity to create design and manufacturing protocols for the creation of engineered polymeric ultrathin film systems (PUFS) may well rest on the development of sophisticated, in-situ diagnostics. The Langmuir/Blodgett deposition technique offers the possibility of providing the foundation for the application of organics to important emerging fields, such as optical computing, electronics, and biotechnology. These applications depend on precise control of materials properties such as positional and orientational order of active moieties, alternation of layers, and thickness. With the need to investigate mixtures and compounds of polymers being deposited in order to create film systems possessing three-dimensional order, it has become evident that methods need to be developed capable of tracking the elastodynamic, hydrodynamic, and electrodynamic behavior of the monolayers as they are extracted from the air/water interface. It is proposed in this project to introduce laser beams at the contact line, as well as at the upper and lower resting positions. Second harmonic generation (SHG), which appears to be a very promising probe, is used here to study the orientation of molecules on the Langmuir layer, as well as to characterize the order of completed film systems of optically highly nonlinear dyes. By comparing the SHG from the Langmuir layer with that obtained at the water contact line on the substrate, and later at the upper resting (drying) position, the PI's are able to measure reorientation of the dye moiety through polarization rotation, changes in area/molecule through amplitude changes, and chemical degradation and drying by examining these same effects on different molecules and substrates. In this initial effort, the PI's plan to attempt to confirm that such measurements are possible, and that dynamics are occurring during time scales which validate the need to pursue further study. If such dynamical changes are evident, accurate monitoring may allow delicate adjustment of trough conditions for improved film quality. These measurements will provide valuable information not presently available concerning the distinctions between the behavior of the early monolayers and that of subsequent layers. The optical return signal will aid in establishing the transitional history of the Langmuir layer as it is transformed into a specific deposited monolayer. If this work is successful, it will open the way to additional optical and infrared spectroscopies capable of detecting subtle changes in conformation and bonding in thin liquid films.
