Synthesis, characterization, and description of influences on the stabilizing activity of antioxidant-functionalized multi-walled carbon nanotubes

Synthesis, characterization, and stabilization tests of two antioxidant (AO) functionalized multi-walled carbon nanotubes (MWCNTs) are presented. Antioxidizing di-tert-butylphenol groups are covalently bonded via two different linkers to the ends and defect sites of MWCNTs. A 40 wt.% degree of chemical functionalization is realized by oxidizing pristine MWCNTs using acid treatment and subsequent catalyzed coupling with the amine-functionalized AOs. Additionally, preparation and full characterization of both AOs, including a five-step synthesis approach with an overall yield of 35%, is described. We show that MWCNT-grafted AOs compounded with isotactic and amorphous polypropylene have moderate or no stabilizing effect against oxidative stress, depending on the method of stabilizer addition. Further, we examine the reason for this weak effect and prove the mechanism of hindered action experimentally.