## 3 Results and Discussions
### Characterization of Materials  
Infrared spectroscopy. Figure 2 shows an example of FTIR-ATR spectra of PEDOT:Triflate composite material (see also Figure S5). There are no substantial differences in the spectra obtained of cellulose fibers and Whatman filter paper substrates, identifying the most intense band in the region between 1180 and 940 cm\({}^{-1}\) attributed to C-O and C-C stretching vibrations [31; 32]. PEDOT-cellulose materials present FTIR peaks at 1518, 1350, and 1220 cm\({}^{-1}\) that can be attributed to the quinoid structure and stretching modes of C=C and C-C in the thiophene ring and the stretching of the C-O-C bond in the ethylenedioxy group of PEDOT, which demonstrates that PEDOT was successfully coated on the cellulose fibers in all composites materials prepared [33; 34]. Other characteristic peaks can be found at around 980, 830, and 695 cm\({}^{-1}\) due to the vibration modes of the C-S bond in the thiophene ring [35]. The FTIR spectrum of PDBProDOT (Figure S6) composite exhibits, in addition to the corresponding peaks associate to the quinoid structure and cellulose fibers as shown for PEDOT composites, the vibration peaks associated to stretching in the alkylendioxy group of the lateral chains at 1017-1048 cm\({}^{-1}\)[36]. Figure 2: FTIR-ATR spectra of Whatman substrate (blue), PEDOT:Triflate (red), and PTfWSp composite material (black). Cross-sectional SEM. The cross-section SEM images of in-situ composite materials were recorded in order to demonstrate the successful polymerization of PEDOT on the surface of the cellulose fibers inside the substrates. Figure 3 shows the cross-sectional micrographs of some examples of composite materials prepared in this work using different cellulosic substrates. Electrical properties. The final purpose of these composite materials is to use them as flexible electrodes for electronic devices. Moreover, having scalability of these materials in mind, the objective of studying different approaches for the preparation of CPs-cellulose composite materials is to obtain a flexible material with good electrical properties with the lowest polymer content. Table 3 contains the results obtained of \(\sigma\) measured by dielectric spectroscopy (bulk conductivity) (Figures S7 and S8) and \(\sigma_{\mathrm{s}}\) measured by the four probe method (surface conductivity). As a reference, values for CPs are also included. Some samples previously described were not measured due to poor mechanical properties that were visually shown in Figure 1. In the case of the \(\sigma_{\mathrm{s}}\), some samples could not be measured due to the high resistance of the sample with the current limits proposed (1-10 mA). Table 3 also includes the polymer content in wt.%, which was calculated using the weight difference of the substrates before and after the CPs incorporation. The significant differences between \(\sigma\) and \(\sigma_{\mathrm{s}}\) values (Figure S9) can be explained due to the well-known anisotropy of PEDOT [37] and the influence of the heterogeneous morphology of the substrates. According to the literature, measurement of \(\sigma_{\mathrm{s}}\) using the four-probe method is recommended for values above \(10^{-2}\) S-cm\({}^{-1}\); therefore, only samples with values beyond this limit were considered (Figure 4) [38]. Moreover, assessing the development of supercapacitors applications, surface conductivity suggests a more reliable and representative conductive mechanism. Thinking  
Figure 3: Cross-sectional SEM micrographs of (**a**,**b**) PTICSp; and (**c**,**d**) PTIWSp. Micrographs (**a**) and (**c**) correspond at 250\(\times\) magnification and micrographs (**b**,**d**) to the enlargement of the yellow boxed area (800\(\times\) magnification). about a real device, the relationship between roughness and electrical surface properties may play a fundamental role as an electrode-electrolyte interface is formed.