Synthesis and spectroscopic analysis of smart photochromic materials

Sol-gel processing was used to dope photochromic materials into metal alkoxide-polymer and pure polymer materials. The films on silicon and quartz substrates were examined, with and without UV irradiation, by UV/VIS spectroscopy, ellipsometry and FTIR. The UV/VIS spectroscopy showed that the doped matrices were photochromic in the visible and near infrared. The ellipsometric data were obtained with a variable angle of incidence spectroscopic ellipsometer (VASE). The Cauchy and a combined Cauchy-Lorentz model were used to fit the unirradiated and irradiated films, respectively. The optical constants of the films showed significant changes upon irradiation. This means that the absorption coefficient and hence the emissivity of the films is being modulated with UV irradiation. The VASE-fitted thicknesses of the films were in the range of 1 to 6 microns. In the FTIR spectra, the spiropyran doped samples have shown IR transmission changes in the two spectral regions (6-7 mu m and 7.5-8.5 mu m) where changes are expected due to band opening. The transmission ratio for UV irradiated to unirradiated samples decreased by as much as about 24% at a particular IR wavelength.