## 3 Results and Discussions
### Characterization of Materials
As explained throughout this work, the absence of dependence is due to the influence of the material preparation on the coating of the fibers for the different cellulosic substrates. From the values shown in Table 4, no dependence is observed either between Sa parameters and PEDOT mass loadings. Composite materials derived from PEDOT:Tosylate prepared by casting possess the lower \(\sigma\)s values (\(\approx\)10\({}^{-2}\) S-cm\({}^{-1}\)) and low polymer content resulting in high values of surface roughness (Sa \(\geq\) 11 \(\upmu\)m). Similarly, PTfCCt presents \(\sigma\)s values in the same order but containing a very high PEDOT mass loading. Independently of the PEDOT source, the use of casting as processing methodology for the in-situ approach has been proven not to be the best option, due principally to the resulted heterogeneous coatings, and despite containing high polymer amounts its \(\sigma\)s is not positively affected. On the other hand, composite materials derivative of PEDOT:Triflate prepared by spray coating present \(\sigma\)s values of at least one order of magnitude higher compared with casting processing. Furthermore, the higher \(\sigma\)s values correspond to composite materials prepared with PEDOT:Triflate which corroborates the successful use of Fe(Trif)\({}_{3}\) as oxidizing agent by using this in-situ approach. Besides, this methodology has allowed to obtain flexible cellulosic composite materials with high \(\sigma\)s and low polymer content, due to effective and homogeneous coating of PEDOT:Triflate throughout the fibers of cellulose during the in-situ polymerization. Correlation displayed by Figure 7b confirms this behavior observed for PEDOT:Triflate-derived composite materials prepared by spray coating with Sa in all the selected composite materials, included for solutions of PEDOT:PSS processed by casting onto substrates of cellulose acetate (PPsACt). Moreover, an inverse trend can be appreciated for all these families of composite materials with Sa values, making a direct relationship of roughness, polymer content, and the corresponding processing conditions with electrical properties. An optimal coating of cellulose fibers during the in-situ polymerization or impregnation process is a key factor for the efficient synergy of properties; flexibility and conductivity, for all prepared composite materials. Depending on the substrate and the in-situ approach, we obtained materials with improved coating efficiency showing a continuous increase in \(\sigma\)s values (from 0.05 to 0.77 S-cm\({}^{-1}\)) as Sa decrease (from 16 to 6 \(\upmu\)m), despite the low PEDOT mass loading (PTfWSp contains 2.7 mg-cm\({}^{-2}\)), and maintaining the flexibility of the cellulosic substrate unchanged. These results show the excellent relationship between PEDOT-mass loading and conductivity with the surface properties and flexibility of the composite material. The in-situ preparation of these composite materials by spray coating has achieved a synergy of properties that makes us face in a very optimistic manner the use of these materials as flexible electrodes accomplishing all the electroactive material to a pseudo-solid electrolyte succeeding a good electrochemical behavior without loss of flexibility.