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Polycarbonate (PC) was reinforced with pristine and chemically modified graphene oxide (GO) to assess its effect on the PC mechanical properties. Commercial graphene with oxygen contents of 4.7 at %, was used as reference to corroborate the affinity of a GO with oxygen content of 25.6 at. % with PC. GO was modified with 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDAC). Commercial graphene, unmodified and modified GO were characterized by FTIR, Raman, XRD and XPS to determine the effects of their structure on the mechanical properties of the reinforced PC. The concentration of graphene oxides in the PC nanocomposites was 0.25, 0.50 and 0.75 wt %. The nanocomposites were characterized by tensile and impact resistance tests as well as by TGA. The distribution of graphene oxides within the PC matrix was evaluated by optical microscopy and scanning electron microscopy. Samples with unmodified GO and commercial graphene showed better dispersion into the polymer matrix than EDAC-modified GO. The unmodified GO increased show increased impact resistance with respect to PC as well as a 291% increment in the elongation at break, with an optimal content of 0.25 wt % of the filler. The EDAC-modified graphene oxide as well as commercial graphene did not increase the impact resistance at any used concentration. The structural and chemical analysis of the EDAC-GO indicate GO reduction during its modification, suggesting that the oxygen functional groups in pristine GO, particularly carboxyl moieties are the responsible for the dispersion and interactions with the polymer and the improvement in mechanical properties. Image 1 • Polycarbonate was modified with commercial graphene, graphene oxide and GO-EDAC. • Young's modulus and tensile strength are not affected with any of the fillers. • PC with 0.25 wt % GO showed a 291% increment in the elongation at break and 28% impact strength. • GO-EDAC is the worst nanofiller dispersion and has the worst mechanical properties. • Carboxyl groups lead to better GO-in-PC dispersion for improvement in mechanical properties. [ABSTRACT FROM AUTHOR]