NANOSTRUCTURES OF COMPLEX POLYANILINE FILMS : EFFECT OF TRANSITION METAL IONS AND APPLIED MAGNETIC FIELDS

Two external factors that control properties and, particularly, architecture of conducting polyaniline films are considered. The first one is metal ions added to the film composition. Different salts of transition metals have been employed as dopants of polyaniline films to induce changes in electrical, spectroscopic and morphological properties of the complex films. The paper describes different tendencies in formation of the complex films and the mechanisms by which the transition metal ions affect their properties. The second factor is an applied magnetic field that affects behavior of both diamagnetic centers of the polymer chain and paramagnetic metal ions. It is shown how the applied magnetic field can effect on morphology and intrinsic conductivity of complex polyaniline films. Introduction. Last years, nano-scale electronics has become a subject of the growing interest and practical use (1,2). One of the main reasons of that interest originates from the fact that an object of a nano-scale dimension represents a qualitatively new level of organization of matter whose properties principally differ from those of the macroscopic world and the world at the atomic level. The nano-physics comprises physical phenomena of objects which fall into the size range between several nanometers to ~100 nm, i.e., the objects which consist of several tens to several thousands of atoms. Such an object usually has properties intermediate between those of the quantum object and the macroscopic one. Molecular electronics is a natural branch of the nano-electronics, since the molecules are naturally occurring nanometerscale structures. Design of nano-structured conducting polymer films or polymer nano-particles with a given architecture is a challenging problem in organic electronics. A certain architecture of the conductive polymer nano-particle functions electronically in a specific manner and serves therefore as a prototype of an element of the future electronic device (3). This discovery encourages development of different techniques to produce polymer nanotubes (4-6). As to the film deposition, in addition to the traditional adsorption at the liquid-solid interface, spin-coating, Langmuir-Blodgett, etc., techniques, different methods have been developed last years, such as the self-assembly technique (7,8), microcontact printing technique (9,10), electrospraying technique (11) to produce patterned conducting polymer films. Addition of another component to the conductive polymer film or blending with another polymer or low-weight substance leads in some cases to the improved film characteristics, particularly mechanical properties, leaving electrical conductivity of the film being of the same order. Our recent attempts were directed to modify polyaniline (PANI) film properties using inorganic salts. The addition of salt ions serves two roles. The first one is doping of the polymer chains, i.e., conversation of the insulating polymer form to the conductive form. The second role is to induce a specific morphology of a film. There exists a further problem how to control the film