Photo- and thermo- oxidative stabilization of polymer-based nanocomposites through the incorporation of CNTs with in-built antioxidant activity

Antioxidant molecules are physically immobilized onto multi-walled carbon nanotubes (CNTs) surface and the resulting hybrid-nanoparticles are used to prepare Ultra High Molecular Weight PolyEthylene-based nanocomposite with enhanced photo- and thermo- oxidation resistance. Natural phenols derivatives, such as quercetin and α-tocopherol, are known to be an excellent antioxidant for polyethylene, but when they are physically immobilized on CNTs the stabilizing activity strongly increase. This is due to a synergic effect stemming from the physical interaction between the antioxidants and CNTs, which cannot provide a similar stabilizing action if used separately. In particular, it is proposed that the process of physical immobilization of the antioxidant molecules causes the formation of structural defects onto CNTs surfaces, thus remarkably improving the nanotubes radical scavenging activity. Similar results have been obtained with CNTs subjected to prolonged ultra-sound treatment, which induces the formation of large amount of structural defects. In all, polymer-based nanocomposites with modulated photo- and thermo-oxidative resistance can be achieved, tuning the CNT radical scavenging properties, which can be rationally controlled by the immobilization of naturally occurring anti-oxidant and by the ultra-sound assisted defects formation.