Electrostatic layer-by-layer assembly of poly(amido amine) dendrimer/conducting sulfonated polyaniline: Structure and properties of multilayer films

The multilayers of poly(amido amine) dendrimer (fourth generation amine-terminated, G4NH(2)) and conducting sulfonated polyaniline (SPANI) were successfully deposited onto solid substrates by alternatively dipping in SPANI and G4NH(2) solutions. Multilayer growth was monitored by ultraviolet-visible absorption spectroscopy and Fourier transform infrared-reflection absorption spectroscopy, which revealed an adsorption-desorption phenomenon, although it was sensitive to the concentration and pH of solutions. The average thickness of the SPANI/G4NH(2) bilayer obtained from X-ray reflectivity is much,smaller than the diameter of G4NH(2) with an ideal spherical structure, suggesting that the dendrimer molecules in multilayers are highly compressed along the surface normal. Electron density profiles indicate that the multilayers are highly interpenetrated, and the thickness and molecular arrangement in the multilayers depend on the pH of G4NH(2) solutions. Cyclic voltammograms of the multilayers in acidic and neutral electrolyte solutions show that the multilayers have good physical and electrochemical stability. The photoelectric conversion response shows cathodic or anodic photocurrent depending on the bias voltage (i.e., on the oxidation state of SPANI). At higher potentials, it shows characteristics of an n-type semiconductor, whereas it behaves like a p-type semiconductor at lower potentials.