Investigation of the Elastic and Structural Properties of Langmuir-Blodgett Films

摘要

Raman and Brillouin scattering, infrared Fournier transform absorption spectroscopy and scanning tunneling electron microscopy have all been used in this program to investigate the elastic and structural properties of Langmuir Blodgett (LB) films, a class of materials which hold considerable promise for many applications in electronics and optics. Many new measurements and discoveries have been made. To summarize: (1) Two step melting of an LB filming was observed for the first time by infrared spectroscopy. The onset of strong disorder in the hydrocarbon tail was found at temperatures lower than those at which the head group lattice melts. (2) Thermal and UV polymerization of LB films was followed spectroscopically and found to lead to equivalent structures. Conditions for polymerization without lattice distortion were found. (3) Scanning tunneling microscopy was used to image LB molecules on the surface for the first time. (4) The elastic properties of a cadmium arachidate LB film were measured for the first time. The shear elastic constant is quite small for a solid film. There is evidence for molecular orientation in the depolarized spectra of the CdA films. Strong similarities in acoustic properties between these LB films and smectic B liquid crystals were found.