POLYELECTROLYTE MULTILAYER ASSEMBLIES CONTAINING NONLINEAR-OPTICAL DYES

An ionene-type polycation incorporating a nonlinear optical chromophor e was synthesized. It was employed for the assembly of alternating pol yelectrolyte multilayers on charged and uncharged substrates, using di fferent organic polyanions as well as montmorillonite clay as anionic counterparts. The assembly process was followed by UV/vis spectroscopy . The influences of the choice of anionic species and of variations in the layer architecture were studied, Different kinds of aggregation w ere observed for different species of polyanions employed, and the inc rease of absorbance with the number of layers proved to be dependent. on the specific multilayer composition. The degree of orientation of t he chromophores was investigated by second-harmonic generation and the nonlinear response was found to depend strongly on the anionic specie s. This result demonstrates that polyelectrolyte multilayers do not ne cessarily have a centrosymmetric structure, as generally assumed.