Variations in the linear charge density of a weak polyacid brought about by controlling solution pH in a layer-by-layer sequential adsorption process were used to systematically control the layer thickness, level of layer interpenetration, and surface wettability of sequentially adsorbed layers of poly(acrylic acid) (PAA) and poly(allylamine) (PAH). The thickness contributed by an individual polyion layer was found to depend primarily on the pH of the polymer's dipping solution and, within the pH range examined, was not influenced by the thickness or level of interpenetration of the previously adsorbed layer. Contact angle and methylene blue adsorption measurements revealed that the deposited layers are typically highly interpenetrated and that the deposition process is a surface charge dominated adsorption process. Using this simple molecular-level blending approach, it is possible to create surfaces with advancing water contact angles that vary from essentially zero (completely wettable surfaces) to as high as 50°, all using the same simple polycation/polyanion combination.

High efficiency, solid-state light-emitting devices have been fabricated from a water soluble, polymeric ruthenium (II) complex, Ru(bpy)3 2+ polyester, via the use of a layer-by-layer processing scheme. Spin-coated devices of this material were found to produce maximum luminance levels of 250−300 cd/m2 with an external quantum efficiency of 0.2% photons/electron. Devices based on sequentially adsorbed layers of the Ru(bpy)3 2+ polyester and poly(acrylic acid), on the other hand, exhibit external quantum efficiencies in the 1−3% range with a maximum light output of 40−50 cd/m2. These high device efficiencies were obtained by optimizing the relative amounts of Ru(bpy)3 2+ polyester and poly(acrylic acid) incorporated into the film via a layer-by-layer molecular-level blending approach. Through this type of control, it was also possible to create compositionally graded heterostructures and to produce devices that emit light only in the forward or reverse bias or that were completely symmetrical (similar light output, current flow, and efficiency in both forward and reverse bias).

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The layer-by-layer self-assembly of a number of different functional dye molecules has been accomplished via the alternate spontaneous adsorption of polyelectrolytes and ionic dyes from dilute solutions. Multilayer thin films containing such functional dyes as pH indicator dyes, infrared absorbing dyes, porphyrin dyes and various fluorescent dyes have been successfully fabricated and their electrical and opt, 2al properties examined. Multilayers containing a newly synthesized ionic ruthenium based polypryidyl dye have been utilized to fabricate light emitting thin film devices with high brightness (ca. 100 cd/m2) at voltages in the range of 5–10 volts. These new light emitting thin film devices exhibit excellent stability when compared to devices based on conjugated polymers such PPV. The fabrication and device evaluation of new heterostructure thin films based on this new light emitting dye as well as the properties of other multilayer thin films containing dye molecules are presented.