Electrochemical polymerisation of 5-amino-1,10-phenanthroline onto different substrates. Experimental and theoretical study

The present work shows that the 5-amino-1,10-phenanthroline (5Aphen) molecule can be electrochemically polymerised, forming a conducting polymer, through potentiodynamic as well as potentiostatic methods onto different electrode substrates: (1) A composite formed by carbon paste in an epoxy matrix, (2) glassy carbon and (3) polycrystalline gold. From the analysis of the experimental potentiostatic current-time plots obtained using electrodes (2) and (3) it is shown that for both cases the formation mechanism of the polymer, (poly5Aphen) involves the simultaneous presence of an adsorption process, which seems predominant at times short enough to the start of the potential jump, and a three-dimensional, 3D, nucleation and growth process limited by the monomer diffusion toward the electrodeʹs interphase. The mechanism suggests that the growth of the polymer takes place via direct incorporation of the monomer species. Studies carried out varying the angular speed of the vitreous carbon rotating disc electrode (RDE) showed that the limiting current increased directly proportional to the square root of the rotation frequency, as predicted by the Levich equation, thus indicating that the possible formation of intermediate oligomer species have a small effect on the polymer growth. A theoretical study of the monomer and some oligomers, through evaluation of the Fukui functions, allowed us to gain insight on the mechanism of polymerization of 5Aphen. It was found a linear oligomer species that adequately describe the experimental features found like the conducting nature of the polymer formed.