## 3 Phase Content and Dispersion of Nano-Inclusions  
PVDF films (neat and hybrid ones) were deposited on conductive substrates using the natural stretching mechanism applied by the spin coating technique, and we adjusted the elaboration parameters (i.e., speed, steps, density of the PVDF-based solution, and temperature) in order to optimize the \(\beta\)-phase content [42]. We present here four different samples: two neat PVDF films (hereafter referred to as PVDF-20 and PVDF-80) with similar thicknesses obtained by the same spin coating process using two different elaboration temperatures (see Supplementary Materials Table S1). The structural and electroactive properties of these two samples were compared to those of PVDF hybrid films with 0.5% wt of non-functionalized nanoparticles (hereafter referred to as NF-PVDF) and to a PVDF hybrid one with 0.5% wt of functionalized nanoparticles (hereafter referred to as F-PVDF). Details on the elaboration and XRD diffraction patterns of the four samples can be found in [42]. The surface microstructure comparison of the four films obtained by SEM and AFM analysis is shown in the Supplementary Materials Figures S1 and S2. The results show a homogeneous morphology of the large surfaces observed by SEM technique and confirmed by local surface AFM measurements. The characteristic micrometric spherulitic structures were visible with additional sub-micron fiber structures in agreement with the previously reported morphology of PVDF films presenting a majority of the \(\beta\)-phase content [48,49]. The whole set of films presented a mean thickness in the range of 75-100 nm and a mean roughness in the range of 3-14 nm. To study the effect of the nanoparticle interface organization on the PVDF \(\beta\)-phase nucleation, FTIR was used, as this method is proven to be as suitable as X-ray diffraction for the determination of the different phases of PVDF. As already reported [42], for the very thin PVDF films, the diffracted intensity was too low. This makes it useful for qualitative identification of the corresponding phase (see Supplementary Materials Figure S3), but it hinders quantitative studies. On the contrary, specific bands of FTIR transmittance in a wavelength range between 500 and 1500 cm\({}^{-1}\) have previously been identified to be clearly characteristic of the different phases' content [13,14] and demonstrated to be able to quantify the electroactive phase content in PVDF materials. We thus recorded the FTIR spectra of the four films at room temperature in the 600\(-\)1500 cm\({}^{-1}\) wavenumber range. A baseline recorded at room temperature was subtracted from the corresponding spectrum using the spectrometer software. We also took into account the Si substrate's transmittance in order to avoid any dependencies of our analysis on the substrate. In Figure 2, we report FTIR normalized spectra presenting the characteristic bands of the \(\alpha\) and \(\beta\) phases for the four films. Several bands located at 840, 870, 1275, 1340, and 1403 cm\({}^{-1}\) were clearly identified and characterized the \(\beta\) phase (see Figure 2) [13; 14; 48]. These bands were related to the sequences of more than three and/or four trans-conformations [13; 14] of the polar phases. In Figure 2, the characteristic absorption peak at 840 cm\({}^{-1}\) was used to quantify the \(\beta\)-phase content, showing similar absorbance characteristics among the four samples. Non-polar \(\alpha\)-phase absorptions were still visible, even though they were less intense, at 766, 795, and 1211 cm\({}^{-1}\). The FTIR spectra also showed the presence of several absorption bands at 1070 and 1175 cm\({}^{-1}\). These latter bands were characteristic of the vibrations of the carbon-carbon skeleton in the polymer [13; 14; 48]. Again, the intensities of these bands seemed not to evolve as a function of the thermal treatment and the presence of the nanoparticles, emphasizing a good organization of the polymer structure for all our samples.