Effect of orientation and order on the functionality of molecular assemblies on surfaces

Abstract

Surface modification of metallic and dielectric substrates can occur through the deposition of pre-formed polymers either by self-assembly (SA) or by the Langmuir-Blodgett (LB) technique. In the latter case the order and orientation of multilayered assemblies can be influenced by the structure of the surface layer. This is particularly evident when LB monolayers of a hemicyanine dye containing an n-alkyl hydrophobic chain are interleaved with monolayers of perdeutero-arachidic acid. Using polarized infrared spectroscopy, the orientation of the individual molecular layers could be determined by monitoring the relative intensity of bands associated with both the CD2 and CH2 sequences. The effect of the spacer layers on the orientation of the hemicyanine molecules was investigated and correlated with the nonlinear optical behavior of these multilayered assemblies.