Multiple adsorption of polythiophene layers on ITO/glass electrodes and their optical, electrochemical, and conductive properties

Polyelectrolyte multilayers containing electrochemically active polythiophe nes have been constructed on ITO/glass substrates using the layer-by-layer adsorption deposition technique. Electrochemically active layers of poly(cy clopentadithienyl-alkylsulfonate) poly(cyclopentadithienyl-alkylammonium), and alpha,omega -bis(carboxyhexyl)sexithiophene were deposited with non-ele ctroactive layers of polyallylamine and polystyrenesulfonate. The first seq uential adsorption of multilayers in which both the polycation and the poly anion are based on the same polythiophene is reported. UV-vis spectroscopy and cyclic voltammetry indicate a linear dependence of the amount of deposi ted polymer on the number of deposition cycles. The rate of deposition depe nds on the oxidation state of the polythiophene being 3 times lower for the oxidized polycationic polymer. Atomic force microscopy characterization of the layers has shown that flat monolayers are deposited with a progressive increase of roughness. Interposition of multiple nonelectroactive layers b etween the electrode and a single external electroactive polythiophene laye r has allowed determination by cyclic voltammetry that each polythiophene l ayer interpenetrates the confining layers up to a three-layer distance. The conductivities of the multilayers along the surface and perpendicular to i t are anisotropic depending on the layer alternation. The photoluminescence properties of the alpha,omega -bis(carboxyhexyl)sexithiophene multilayers are the same for vacuum-deposited polycrystalline layers.