## 3 Results and Discussion
This observation is in good agreement with the XPS results (Figure 4b): the C1s spectrum of the GOs deconvoluted to 37.7 at % of C-C, 52.8 at % of C-O, and 9.5 at % of C=O bonds, whereas L-GO showed 34.6 at % of C-C, 57.4 at % of C-O, and 8.0 at % of C-O bonds. The ratio of C=O/C-C was 1.4 and that of C-O/C-C was 0.3 for GOs; these values were 1.7 and 0.2 for the L-GOs, respectively, which indicated that L-GO flakes have more epoxide functional groups and fewer carboxylic functional groups than GO flakes. After HI reduction, due to the removal of oxygen functional groups and restoration of graphitic structures during chemical reduction, the intensities of the C-O and C=O bonds dramatically decreased and that of the C-C bonds increased for both the GO and L-GO films [29]. Figure 3: (**a**) Schematic of preparation of graphene-based films from liquid crystal GO suspensions. Gray and red circles indicate carbon atoms and functional groups, respectively. (**b**) Photograph of GO and L-GO films before and after reduction. (**c**) Structural change in graphene-based films by HI reduction: schematic illustration (top), and cross-sectional SEM images (bottom). Scale bars are 100 \(\upmu\)m, and insets are high magnification (\(\times\)10,000) images of the regions marked with white rectangles. (**d**) XRD spectra of GO and L-GO films before and after hydrogen iodide (HI) reduction. The mechanical and electrical properties of the GO and L-GO films were evaluated (Figure 5a,b). The L-GO film exhibited 1.32\(\times\) higher modulus (3.7 GPa), 1.98\(\times\) higher ultimate tensile strength (20.37 MPa), and 1.28\(\times\) higher elongation at break (0.55%) than the GO film (modulus: 2.8 GPa, ultimate tensile strength: 10.28 MPa, elongation at break: 0.43%). These mechanical properties of both the GO and L-GO films were greatly improved by HI reduction: 8.3 GPa modulus, 130.76 MPa ultimate tensile strength, and 3.09% elongation at break for the L-GO film, and 5.7 GPa modulus, 47.00 MPa ultimate tensile strength, and 1.53% of elongation at break for the GO film were obtained. The reduced L-GO film also exhibited only 37% (8.2 \(\Omega\)/sq, 340 S/cm) of the GO film's sheet resistance (21.9 \(\Omega\)/sq, 120 S/cm), which is a 2.83\(\times\) higher electrical conductivity. These large differences in both mechanical and electrical properties between GO and L-GO films were mainly due to differences in the size of the flakes that composed each film: the average flake size in the L-GO film was about four times larger than that of GO films. In general, because graphenes are mechanically stiff flakes having high electrical conductivity, loads or electrons can be efficiently transferred within the graphene flakes. In contrast, at the grain boundaries, which are interconnecting regions between different graphene flakes, scattering of loads or electrons can occur due to the presence of structural discontinuity at these regions [30; 31]. As the flake size decreases, the fraction of grain boundaries in the film increases, which can act as scattering centers of loads and electrons, degrading both mechanical and electrical properties. Therefore, the L-GO film showed better mechanical properties than the GO film due to less scattering of loads and electrons at grain boundaries. Compared to our reduced L-GO film, the state-of-the-art graphene film in which the GO flakes with a lateral size of 5 \(\upmu\)m are strongly interconnected via physical crosslinking by evaporation of GO hydrogels showed better mechanical and electrical properties (ultimate tensile strength = 614 MPa and electrical conductivity = 802 S/cm) [32]. However, we expect our larger GO flakes will result in GO film with better mechanical and electrical properties if the interface between graphene flakes improves. Figure 4: (**a**) FTIR spectra of GO and L-GO films. XPS C1s spectra: (**b**) GO, (**c**) L-GO, (**d**) reduced GO, and (**e**) reduced L-GO. (**f**) UV-VIS absorption spectra of GO and L-GO films before and after reduction.