**2.1. p-doping**

When the polymer chains are oxidized, consecutive electrons are removed from each chain generating an excess of positive charges (holes) along the chains. This excess of positive charges (lack of electrons) promotes the repulsion between the polymeric chains and the generation of free volume between them. This free space is occupied by anions arriving from the solution to compensate the emerging positive charges (keeping the electroneutrality) and solvent molecules to keep osmotic pressure balance (Huang et al., 1986; Otero, 1999; Tsai et al., 1988).

When the polymer is generated in the presence of small anions, they can be exchanged by other small anions present in solution by electrochemical reactions so a prevailing exchange of anion occurs during reaction:

$$n\left(\operatorname{Pol}^{0}\right)\_{s} + n\left(\operatorname{A}^{-}\right)\_{sol} + m\left(\operatorname{Solv}\right)\overbrace{\operatorname{Cond}^{n+}}\left[\left(\operatorname{Pol}^{n+}\right)\_{s}\left(\operatorname{A}^{-}\right)\_{n}\left(\operatorname{Solv}\right)\_{m}\right]\_{gel} + n\left(e^{-}\right)\_{metal} \tag{1}$$

where the different subscripts mean: *s,* solid; *sol*, in solution; *gel* indicates that the material is a gel formed by oxidized polymeric chains (Poln+) generated after the extraction of *n* electrons (*e-* ) through the metal (indicated by subscript *metal*) from neutral polymer chains (Pol0), *n* anions (A- ) coming from the solution to keep the gel electroneutrality and m molecules of solvent (*Solv*) required to keep osmotic pressure balance.

When the polymer is generated in the presence of a macroanion, due to its volume and the interaction with polymer chains, this macroanion cannot be exchanged by the electrochemical reaction keeping trapped inside the polymer film. So, in order to keep the electroneutrality, smaller cations are exchanged with the solution during the reaction:

$$\left[ \left( \operatorname{Pol}^{\otimes} \right) \left( \operatorname{MA}^{-} \right)\_{n} \left( \operatorname{C}^{+} \right)\_{n} \left( \operatorname{Svdv} \right)\_{n} \right]\_{gl} \xleftarrow{\prod} \xleftarrow{\prod} \left[ \left( \operatorname{Pol}^{\ast \ast} \right) \left( \operatorname{MA}^{-} \right)\_{n} \right]\_{gl} \\ + n \left( \operatorname{C}^{+} \right)\_{sd} + m \left( \operatorname{Svdv} \right) + n \left( \operatorname{\epsilon}^{-} \right)\_{\operatorname{matl}} \\ \tag{2}$$

where MA is the macroanion trapped inside the polymer film and C+ are cations exchanged in order to keep the electroneutrality.

Usually, the real redox process is not as easy as expressed by reactions (1) and (2): anions and cations are exchanged simultaneously (Hillman et al., 1989; Inzelt, 2008). Usually one of the previous interchanges prevails supporting the greater percentage of charge balance (Kim et al., 2010; Lyutov et al., 2011; Orata & Buttry, 1987; Torresi & Maranhao, 1999).
