Phenolic antioxidants based on calixarene: Synthesis, structural  characterization, and antioxidative properties in natural rubber

Hongqiang Li, Yong Zhong, Wenjian Wu, Lin Zhang, Xuejun Lai, Xingrong Zeng*

Abstract: C-methylcalix[4]resorcinarene (CMCR) was first synthesized by condensation reaction between resorcinol and acetaldehyde, and then used as functional monomer to prepare two CMCR derivatives including C-methylcalix[4]resorcinarene-1 (CMCR-1) and C-methylcalix[4]resorcinarene-2 (CMCR-2) with four ethoxymethyl chains and four hexylthiolmethyl chains, respectively. The structures of CMCR and its derivatives were confirmed by Fourier transform infrared (FT-IR) spectroscopy and high-resolution mass spectrometry (HRMS). Thermogravimetric analysis (TGA) revealed CMCR, CMCR-1, and CMCR-2 had superior thermal stability than commercial antioxidant 2,6-Di-tert-butyl-4-methylphenol (BHT). Oxidation induction time and accelerated thermal aging tests indicated that CMCR-2 exhibited excellent antioxidative property in natural rubber (NR), which was due to multiphenol groups, big steric hindrance, and synergistic effect between thiother and hindered phenol. Importantly, CMCR-2 also possessed outstanding extraction resistance.

论文链接：http://dx.doi.org/10.1002/app.45144