Studies of orientation and order of interleaved Langmuir-Blodgett films of a hemicyanine dye

Abstract

Langmuir-Blodgett (LB) multilayers of a hemicyanine dye in the Z-type configuration (head group towards substrate) have been made with and without interleaving layers of perdeuterated arachidic acid or cadmium arachidate. Polarized IR spectroscopy studies show that LB layers of hemicyanine without interleaving spacer layers lose their registration with the surface of the substrate after only a few layers are deposited. Hemicyanine layers interleaved with spacer layers maintain an approximately fixed orientation with respect to the surface. Deuteration of the interleaving layers permits IR differentiation of the hydrocarbon tails of the dye and the fatty acid or salt so that the orientation and order of each molecule can be separately measured. The choice of interleaving spacer layer, arachidic acid or cadmium arachidate, can be used to change the orientation of hemicyanine with respect to the surface. © 1989.