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In this work, we designed and studied two synthetic routes, based on modified Hummers method, to obtain graphene oxide (GO), and investigated their influence on the performance of polypropylene (PP)/GO nanocomposites. The two synthetic routes differed in the application condition of the oxidizing agent, potassium permanganate (KMnO4), which was added either as a powder (GO‐P) or as a water solution (GO‐S). This apparently subtle synthetic change yielded GOs with different degrees of oxidation and particle sizes, where GO‐P presented a higher oxidation degree and smaller particles. The different GOs were then melt‐blended with PP and the correlation between their different chemical/morphological structures and the nanocomposites' thermomechanical/rheological properties were evaluated. The milder oxidation process suffered by GO‐S, and consequent less hydrophilic character, yielded a PP/GO‐S nanocomposite with improved performance as the consequence of a better matrix/filler chemical affinity, mainly in compositions with lower GO‐S contents. The thermal stability was increased by more than 10°C when 0.1 wt% GO‐S was inserted into PP. When compared to the composition with 0.1 wt% GO‐P, the increase was 13°C. Reinforcing effects were also observed in that sample (with 0.1 wt% GO‐S), which exhibited the highest storage modulus and complex viscosity. These results suggest that tailoring the GO's oxidation degree and morphology is a key point to obtain an ideal interfacial interaction between phases.

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oxide dispersion state in polystyrene-based composites below percolation threshold via linear melt rheology. Rheol Acta 60, 209-218 (2021).