DETERMINATION OF OPTICAL-CONSTANTS OF MOLECULAR FILMS ASSEMBLED VIA ALTERNATE POLYION ADSORPTION

The optical properties of ordered multilayer assemblies produced by alternately dipping a substrate into polycation and polyanion solutions are investigated by using a planar optical waveguide as substrate and measuring the mode indices of the guided waves. The layers show a distinct positive birefringence, from which it is inferred that the polymer chains prefer to be oriented perpendicular to the interface (loops). If the films are equilibrated in water, the anistropy diminishes and the films are somewhat expanded. The kinetics of the assembly process was also studied by arranging for a flux of the polyion solution to pass over the waveguide surface while measuring the mode indices.