LANGMUIR-BLODGETT-FILMS OF RETINAL DERIVATIVES

We report characterization studies of Langmuir films and Langmuir-Blod gett multilayers of 13-cis-retinoic acid, 13-cis-retinal aldehyde, all -trans-retinoic acid, and all-trans-retinol palmitate. We have examine d the stability of the floating monolayers prepared on an air-water in terface, and the values estimated for the mean molecular areas before collapse are consistent with previous results for other retinal deriva tives. After successful transference of the monolayers to form Langmui r-Blodgett films on different solid substrates, we have applied standa rd infrared spectroscopic techniques to investigate the structural org anization of the deposited multilayers of the latter three compounds. By combining the information gathered from the isotherm compression cu rves of the Langmuir films to the analysis of the relative intensities of characteristic retinal peaks on the grazing angle and attenuated t otal reflectance spectra of the solid films, we have qualitatively est imated the orientation of the deposited molecules relative to the subs trate. We comment on the implication of these results for the use of L angmuir-Blodgett films of retinal derivatives in molecular electronic devices.