MOLECULAR-LEVEL PROCESSING OF CONJUGATED POLYMERS .1. LAYER-BY-LAYER MANIPULATION OF CONJUGATED POLYIONS

The layer-by-layer molecular-level manipulation of conjugated polyions has been successfully utilized to fabricate ultrathin multilayer film s and multilayer heterostructures. Through a process involving the alt ernate spontaneous adsorption of oppositely charged polymers from dilu te aqueous solutions, multilayer thin films were fabricated from a var iety of different bilayer combinations including conjugated/nonconjuga ted polyion bilayers, conjugated/conjugated polyion bilayers, and prec ursor polymer/conjugated polyion bilayers. UV-vis absorbance measureme nts revealed that in all cases the bilayer deposition process was line ar and highly reproducible from layer to layer. Kinetic studies showed that the equilibrium adsorption of a polyion layer is reached within about 10 min and the process can be carried out onto different substra te surfaces. The typical bilayer thickness ranges from approximately 1 0 to 25 Angstrom and can be readily controlled by variations in such p arameters as solution concentration, pH, doping level, and ionic stren gth.